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Clearing and containing floats

From: Dreamweaver CS5 Essential Training

Video: Clearing and containing floats

There will be times when creating float- based layouts that you want the floated elements to no longer affect the elements that follow them. In our own layout for example, the mainContent region and the sidebar are using floats to achieve a two-column layout. We don't want or even need the footer to be overlapped by our floated elements. Towards that end we will apply a clear to our layout. Clearing floats is an essential technique for achieving reliable float-based layouts. It's your way of saying, "that's it." "Those floated elements shouldn't float any element past this point." The clear CSS property has three possible values, left, right and both.

Clearing and containing floats

There will be times when creating float- based layouts that you want the floated elements to no longer affect the elements that follow them. In our own layout for example, the mainContent region and the sidebar are using floats to achieve a two-column layout. We don't want or even need the footer to be overlapped by our floated elements. Towards that end we will apply a clear to our layout. Clearing floats is an essential technique for achieving reliable float-based layouts. It's your way of saying, "that's it." "Those floated elements shouldn't float any element past this point." The clear CSS property has three possible values, left, right and both.

By clearing to the left or to the right, you're essentially saying that nothing can float to the left or right of the cleared element. A clear value of both says that no element may float the cleared element, whether it's to the right or to the left. Once floats are cleared, normal document flow continues. And cleared elements will continue to push down in response to the elements above them, even floated elements. In this sample layout we are going to clear the footer element, which will move it down below our floated elements into the desired location.

So let's take a moment to review our page structure. And here I have the clearing.htm file open. So we have a wrapper div tag, which wraps all the other content on the page. We are using auto margins, so that the wrapper is centered on the page regardless of the size. Now inside the wrapper div tag, we have a div with an ID of header. It's followed with a div with an ID of mainContent. Further down the page we have a div with an ID of sidebar. And then finally we have a div with an ID of footer.

Now as you can tell we have some very basic CSS properties set here. We have some height set, we have background colors, we have some text colors, but other than that we really aren't doing anything with the layout. So I am going to scroll back up to the top and we are going to start our layout by floating the mainContent. Now in this case we want the mainContent to be on the right-hand side and we want the sidebar to be on the left-hand side. Now there are a couple of different ways that we can do this. As a matter of fact if you look at two float-based layouts that are exactly the same, chances are their CSS might be significantly different.

So there are a lot of different techniques for doing what we are about to do here. I am going to select the #mainContent selector over here in the CSS Styles panel and I want to add a property to that. I am going to go ahead and the float property and I am going to float that to the right. That is going to float the mainContent over to the right-hand side. And you can see the sidebar moves up to occupy the space that the mainContent used to be in. Now one thing that you're really not seeing here is that if the mainContent's background color was transparent, you would actually see that sort of light periwinkle, I guess, sidebar color go up underneath the mainContent.

So there is actually overlap going on here now. Now one thing I neglected to mention earlier is that our wrapper div tag is 800 pixels wide. So now when we put our mainContent on the right-hand side and our sidebar on the left-hand side, one of the things that we want to do is set a width for those that is going to calculate out to that 800 pixels wide of our wrapper. That way we know exactly how much area we have in the mainContent and the sidebar for any content that we may place in there later.

So I am going to go back to our mainContent and I am going to add a property to this and I am going to add the width property. And in this case I'm going to make it 500 pixels wide. So that extends the mainContent out a little bit. And now we see the sidebar on the left side, the mainContent on the right-hand side. Now I like to point out one more thing too. If you're going is floating for layouts, whenever you float an element a best practice is to establish a width for the element as well. That is going to prevent a number of problems in certain browsers.

All right next I want to go down to my sidebar. I am going to select my sidebar and I am going to click to add a property here. I am going to add the float property. And this time instead of floating to the right, I am going to float the sidebar to the left. It moves it over to left-hand side of the page. And now the sidebar is on the left all the way up against the edge of its parent element, which in this case is the wrapper. The mainContent is floated to the right all the way up against its parent element edge, which in this case is the wrapper. Now the sidebar is a lot narrower than mainContent.

But we still need to increase its width a little bit just so we don't have this big gap in the middle, as we have here. Now you might be wondering, hey when is he going to say something about that footer? Yeah, the footer does not look right at all. Let's finish off our sidebar and we will talk about what is going on with that footer. So I am going to add a property here and I want to go ahead and add a width value and I am going to give it 280 pixels worth of width. Those values were arrived at in thinking about what I wanted for this particular layout. We have 800 pixels worth of space from side to side here.

By giving 500 pixels here and 280 pixels here we are left with a total of 20 pixels. That 20 pixels becomes the gutter between the sidebar and the mainContent region. So in this case there is no need for us to worry about padding or margins to try to keep those two elements away from each other. The width is going to do it for us. Now back to that poor footer. Okay, so now it's even worse because the footer doesn't have any room to show up. When we scroll down the text of the footer is actually down here. You can't see it because it's white and it is on the white background of the wrapper div tag.

However, the sort of brown background color of the footer is readily apparent. So what happens? Well the footer is going to move up because two elements above it are floated. So it moves up to occupy the space that those elements used to occupy in the normal document flow. So our normal document flow now just says header and footer. It doesn't say header mainContent sidebar footer because mainContent and sidebar are floated and thus removed from the normal document flow. So in order to get our footer to locate in the right place, that would be at the very bottom of the layout down here, we need to re-establish that normal document flow.

And the way to do that is by using clearing. So I am going to go to my footer selector over here in CSS Styles. I am going to add a property to that and I am going to add a clear property. Now if I grab the pull down menu for clear, I can see that I have left, right and both. Now the mainContent is floated to the right and the sidebar is floated to the left. So I really can't choose one over the other. I need to go ahead and in this case choose both. So I am going to choose both and he,y look what happens.

Our footer reappears at the bottom of the page because now we have re-established normal document flow. The footer is no longer allowing any element to float to its left. And it's no longer allowing any element of float to its right. Because of that normal document flow is re-established. So essentially what happens is the header is in normal document flow. mainContent and sidebar temporarily interrupt that as one floats to the right and one floats to the left. But then the footer re-establishes normal document flow by clearing the floats and saying no, I'm not going to be affected by either of those two guys above me.

Now the really nice thing about this particular technique is that if the height of the mainContent region or the height of the sidebar increases, the footer is going to continue to push down the page, because it will never allow one of the two of them to float. So for example, if I go to mainContent and I make its height say 600 pixels, and if we scroll down we can see that the mainContent is pushing the footer down. This is exactly what we need for a two- column layout that has a header and a footer. So by clearing floats we can re- establish normal document flow, contain floats, and help our layout take shape.

If you become familiar with these techniques, you'll understand how the overwhelming majority of CSS-based layouts are created. Now keep in mind this is a very simple, very basic layout, but also an amazingly common one. A header, two columns of content, and a footer has become a standard for many types of web pages. Using floats and clearing them when necessary is a quick and easy way to achieve most of your layout requirements. Of course we've just scratched the surface of what you need to know when floating elements.

For more information on floats and clearing and containing those floats please consult the other CSS titles in the lynda.com Online Training Library. I will cover floats and controlling them in much more detail in my Dreamweaver CSS Essential titles. Now that we've discussed floats, we are going to discuss using the CSS position property to tweak our layouts. And increase the control we have over individual elements within our pages.

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This video is part of

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Dreamweaver CS5 Essential Training

135 video lessons · 88882 viewers

James Williamson
Author

 
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  1. 2m 57s
    1. Welcome
      1m 8s
    2. Using the exercise files
      1m 49s
  2. 7m 50s
    1. What is Dreamweaver?
      3m 16s
    2. Learning web design
      2m 22s
    3. Current web standards
      2m 12s
  3. 43m 9s
    1. The Welcome screen
      4m 5s
    2. Windows and Mac interface differences
      2m 23s
    3. The Application toolbar
      4m 7s
    4. The Document toolbar
      4m 40s
    5. Arranging panels
      8m 19s
    6. Managing workspaces
      7m 32s
    7. The Properties Inspector
      5m 54s
    8. The Insert panel
      6m 9s
  4. 25m 45s
    1. Basic site structure
      3m 11s
    2. File naming conventions
      1m 49s
    3. Defining a new site
      4m 35s
    4. Managing sites
      4m 51s
    5. Managing files and folders
      6m 36s
    6. Working with browsers
      4m 43s
  5. 27m 21s
    1. Creating new documents
      5m 16s
    2. New document preferences
      3m 6s
    3. Setting accessibility preferences
      4m 56s
    4. Working with starter pages
      3m 46s
    5. Managing starter pages
      10m 17s
  6. 30m 2s
    1. Basic tag structure
      2m 15s
    2. Adding structure to text
      8m 20s
    3. Creating lists
      9m 59s
    4. Getting text into Dreamweaver
      5m 59s
    5. Importing Word documents
      3m 29s
  7. 1h 17m
    1. Understanding style sheets
      2m 16s
    2. The anatomy of a CSS rule
      1m 48s
    3. Setting CSS preferences
      6m 36s
    4. The CSS Styles panel
      10m 2s
    5. Controlling CSS through the Properties Inspector
      5m 14s
    6. Using the Code Navigator
      7m 21s
    7. Using CSS Enable
      6m 45s
    8. Understanding element selectors
      8m 11s
    9. Understanding class selectors
      8m 49s
    10. Understanding ID selectors
      5m 59s
    11. Understanding descendant selectors
      6m 51s
    12. Attaching external style sheets
      7m 44s
  8. 1h 47m
    1. Working with units of measurement
      7m 11s
    2. Declaring font families
      9m 39s
    3. Controlling font sizing
      9m 9s
    4. Controlling weight and style
      8m 0s
    5. Controlling line height
      8m 29s
    6. Controlling vertical spacing with margins
      12m 3s
    7. Controlling spacing with padding
      5m 39s
    8. Aligning text
      8m 26s
    9. Transforming text
      5m 36s
    10. Writing global styles
      15m 42s
    11. Writing targeted styles
      17m 37s
  9. 1h 32m
    1. Understanding image types
      5m 3s
    2. Managing assets in Dreamweaver
      12m 51s
    3. Setting image accessibility preferences
      4m 20s
    4. Setting external image editing preferences
      3m 52s
    5. Placing images on the page
      7m 37s
    6. Photoshop integration
      5m 54s
    7. Modifying Smart Objects
      5m 51s
    8. Alternate Photoshop workflows
      8m 8s
    9. Modifying image properties
      11m 14s
    10. Styling images with CSS
      7m 11s
    11. Using background graphics
      9m 3s
    12. Positioning background graphics
      11m 6s
  10. 55m 16s
    1. Link basics
      3m 37s
    2. Setting site linking preferences
      2m 14s
    3. Creating links in Dreamweaver
      11m 1s
    4. Absolute links
      5m 8s
    5. Using named anchors
      11m 19s
    6. Linking to named anchors in external files
      2m 44s
    7. Creating an email link
      5m 24s
    8. Creating CSS-based rollovers
      13m 49s
  11. 1h 34m
    1. CSS structuring basics
      2m 56s
    2. The Box Model
      13m 21s
    3. Understanding floats
      6m 53s
    4. Clearing and containing floats
      8m 56s
    5. Using relative positioning
      4m 8s
    6. Using absolute positioning
      7m 18s
    7. Creating structure with div tags
      12m 7s
    8. Styling basic structure
      10m 34s
    9. Creating a two-column layout
      10m 37s
    10. Using Live View and CSS Inspect
      7m 51s
    11. Using Browser Lab
      9m 39s
  12. 56m 22s
    1. Reviewing table structure
      7m 41s
    2. Importing tabular data
      5m 13s
    3. Creating accessible tables
      9m 56s
    4. Using thead and tbody tags
      4m 0s
    5. Basic table styling
      8m 45s
    6. Styling table headers
      7m 52s
    7. Styling column groups
      4m 22s
    8. Creating custom table borders
      5m 1s
    9. Styling table captions
      3m 32s
  13. 1h 43m
    1. How forms work
      3m 0s
    2. Reviewing form design
      3m 2s
    3. Creating accessible forms
      7m 33s
    4. Setting form properties
      4m 6s
    5. The fieldset and legend tags
      4m 32s
    6. Inserting text fields
      5m 58s
    7. Inserting list menu items
      5m 26s
    8. Inserting checkboxes
      7m 50s
    9. Inserting radio button groups
      6m 22s
    10. Inserting text areas
      4m 12s
    11. Inserting submit buttons
      3m 37s
    12. Basic form styling
      12m 0s
    13. Form element styling
      8m 52s
    14. Styling form layout
      11m 49s
    15. Adding form interactivity
      2m 47s
    16. Using Spry validation widgets
      12m 49s
  14. 1h 23m
    1. Planning for templates
      10m 51s
    2. Creating a new template
      10m 37s
    3. Using editable attributes
      13m 43s
    4. Creating optional regions
      6m 23s
    5. Creating new pages from a template
      9m 17s
    6. Applying templates to existing pages
      6m 9s
    7. Working with nested templates
      7m 56s
    8. Working with repeating regions
      12m 58s
    9. Modifying templates
      5m 41s
  15. 40m 14s
    1. Behaviors overview
      3m 47s
    2. Hiding and showing elements
      9m 18s
    3. Spry overview
      4m 4s
    4. Using Spry widgets
      11m 36s
    5. Adding Spry effects
      3m 6s
    6. Using the Widget Browser
      8m 23s
  16. 28m 18s
    1. Inserting Flash files
      5m 4s
    2. Setting properties for Flash
      6m 27s
    3. Dreamweaver and Flash integration
      6m 6s
    4. Encoding Flash video
      6m 10s
    5. Adding Flash video
      4m 31s
  17. 45m 28s
    1. Running site-wide reports
      6m 33s
    2. Checking for broken links
      5m 41s
    3. Checking for browser compatibility
      8m 3s
    4. Adding remote servers
      8m 0s
    5. Uploading files
      7m 20s
    6. Managing remote sites
      9m 51s
  18. 34s
    1. Goodbye
      34s

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