Easy-to-follow video tutorials help you learn software, creative, and business skills.Become a member

Float containment

From: CSS Web Site Design

Video: Float containment

What you see here is a situation where I've unfloated the columns for a moment and I've enclosed them in a container div, this is just generally what this sort of thing is called. There's a div that begins right before the content div and it ends right after the end of the sidebar div and these things usually have an ID of container. So there you go, div id equals container. That begins as I say before the content and it ends right after the end of the sidebar.

Float containment

What you see here is a situation where I've unfloated the columns for a moment and I've enclosed them in a container div, this is just generally what this sort of thing is called. There's a div that begins right before the content div and it ends right after the end of the sidebar div and these things usually have an ID of container. So there you go, div id equals container. That begins as I say before the content and it ends right after the end of the sidebar.

And this is the background color that I've given it. Now, the reason that these columns are floating is that I've actually written a rule to override the built-in float styles and let me get rid of that now, so that they actually float into place the way they are supposed to and when I hit Reload, there they are. But the container disappeared. Ok, that's weird. Why did that happen. That actually happened, because it collapsed down to have no height at all. So the thing about floats is they don't occupy the normal flow of the document.

The normal flow of the document would be the unfloated, unpositioned, just very generic float of the document, for example this is all normal flow. All right. This is mostly non-normal float, it's mostly floated stuff, because we floated the content, we floated the sidebar and that's all not in the normal flow. In fact, the one thing that is in the normal flow here, pretty much is the footer. Also some aspects of the masthead. So, if you have something like a div, that's containing two other divs and you float both those divs, than the container div has no normal float content, and so it has no height, it has zero height. Now, you might wonder why in the name of all those holly, that makes any sense at all and actually makes a lot of sense if you look at the tea kettle image that we floated to the left, remember that's an image inside the first paragraph, that's then been floated to the left and it's sticking out of that first paragraph.

If it didn't, if elements always grew to contain floats that were inside of them, then what we would have is the first paragraph, and there would be a big blank space before the next paragraph happened, because the paragraph containing that floated image would have to expand the containment. That would be horrible, nobody would like that. So, because floats were really only intended to do things like taking image or some other element, put it to the side and let other text flow around it, that's how they're written, but when it comes to layout, that's not what we want, right. We want this container div to surround visually the two floated columns. So, there are a couple of ways to address this.

Perhaps the most obvious one is the fact that floated elements do grow to contain any floats that they contain. So if we were to float our container then, it would grow to contain the floated columns. If we hit Reload, it's back. There it is, you can see it, it's wrapped all the way around, but there is a potential problem there, which is that, let's say, instead of the background I wanted to do, I'm going to use red, because it will stand out.

That's all fine, but then we can't always assume that the two columns are going to be quote, unquote, 100% wide and push all the way out to the edges so what we'll need here really is, if we wanted to make sure, we might say with 100% and that would make this container nice and wide, but notice what just happened. It just got wider than the actual browser window. That's because if you recall, from the first video in this chapter, width is the content width and then any borders or padding beyond that are added to it, so this is now actually four pixels beyond the right edge of the browser window and that will be two pixels of border on either side.

That's not really what we wanted. So maybe there's another way, one where we can sort of let it grow out to the maximum extent, or basically where we can return it to the normal flow and yet think a way into having it contain floats and actually there is such a way. So instead of float left, what we're going to do is overflow auto, and we need to get rid of the width as well, hit Reload, then there we go.

The reason that this is more desirable is that because the div is back into the normal flow is not being floated, then, because of the way that CSS rules are written, that will always expand to be as wide as it can be. Officially speaking it will always expand to fill its parent element, which in this case is the body. But since we didn't explicitly give it a width of 100%, then it expands as much as it can, including things like padding and borders and even margins so the content gets squeezed down a little bit, if necessary in this case.

So that's normal flow behavior, which is not how floats work, as we saw before, but the reason that it's growing, even though it's in the normal floats, growing to contain its floats is that it's been set to overflow auto. Overflow is property that controls how content is drawn if it happens to be taller than its actual parent. So, you could for example say overflow hidden and then if any of this content happen to stick out of the container div, then it would just get clipped off, it would be hidden. That's all interesting, but you might wonder why in heck, the results of overflow auto, would be to grow to contain floats and as it turns out that's because of, a sort of an obscure corner of the CSS specification, which says, effectively that, I mean it doesn't come right out and say if there are floats then the overflow auto means that a normal flow element will grow to contain them but because the way our flow auto was described, this is one of the things that it needs to do. So, if you want to track down the descriptions of how overflow works in the CSS specification, you can certainly do that, or you can just sort of accept that this is one of those things that just works by magic and go with it. So if you want to have an element that contains floats that are within it like this container div is doing here, those are your two primary choices, either to float the container, or don't float it and set it to the overflow auto.

Show transcript

This video is part of

Image for CSS Web Site Design
CSS Web Site Design

73 video lessons · 61278 viewers

Eric Meyer
Author

 
Expand all | Collapse all
  1. 14m 34s
    1. Welcome
      28s
    2. What is CSS?
      5m 34s
    3. Design tour
      2m 38s
    4. Using the exercise files
      1m 20s
    5. Installing the Web Developer toolbar
      4m 34s
  2. 25m 56s
    1. XHTML essentials
      3m 55s
    2. CSS essentials
      5m 17s
    3. Embedded style sheets
      2m 20s
    4. Linking a style sheet
      2m 19s
    5. Linking to multiple style sheets
      2m 20s
    6. Using linked and embedded style sheets together
      4m 21s
    7. Using imported style sheets
      5m 24s
  3. 57m 48s
    1. ID selector essentials
      6m 38s
    2. Class selector essentials
      4m 9s
    3. Best practices for classes
      4m 52s
    4. Grouped selection
      4m 2s
    5. Descendant selectors
      6m 44s
    6. The sources of style
      6m 38s
    7. Specificity
      8m 21s
    8. Making things important
      4m 32s
    9. Inheritance essentials
      5m 12s
    10. Making things really unstyled
      4m 2s
    11. User style sheets
      2m 38s
  4. 39m 3s
    1. Box model essentials
      7m 35s
    2. Simple floating
      5m 3s
    3. Using float for layout
      5m 5s
    4. Fixing column drop
      5m 35s
    5. Clearing essentials
      4m 20s
    6. Float containment
      6m 35s
    7. Creating a navbar from a list
      4m 50s
  5. 38m 3s
    1. Coloring text
      4m 13s
    2. Defining color in CSS
      8m 12s
    3. Coloring backgrounds
      6m 35s
    4. Applying background images
      4m 19s
    5. Manipulating the direction of background images
      2m 52s
    6. Positioning backgrounds
      7m 23s
    7. Background shorthand
      4m 29s
  6. 58m 28s
    1. Altering line height
      7m 32s
    2. Font style and weight
      5m 45s
    3. Sizing fonts
      9m 59s
    4. Using font families
      10m 38s
    5. Font shorthand
      6m 5s
    6. Justifying text
      4m 56s
    7. Vertically aligning text
      4m 22s
    8. Transforming text
      3m 49s
    9. Text decoration
      5m 22s
  7. 44m 40s
    1. Margin essentials
      14m 21s
    2. Adding borders
      6m 52s
    3. Padding
      9m 17s
    4. Using negative margins
      7m 19s
    5. Margin collapsing
      6m 51s
  8. 20m 38s
    1. Styling tables and captions
      5m 23s
    2. Styling table cells
      6m 30s
    3. Styling a column with classes
      4m 51s
    4. Styling links inside table cells
      3m 54s
  9. 30m 40s
    1. Styling for specific mediums
      4m 3s
    2. Creating a print style sheet
      6m 35s
    3. Hiding layout for print
      4m 11s
    4. Styling for print
      6m 34s
    5. Complex styling for print
      4m 37s
    6. Creating a footer
      4m 40s
  10. 37m 23s
    1. Getting started
      1m 11s
    2. Setting global styles
      4m 4s
    3. Defining masthead and navbar colors
      3m 27s
    4. Layout of the navlink bar
      3m 38s
    5. Using columns
      4m 49s
    6. Setting content styles
      1m 53s
    7. Creating the sidebar boxes
      5m 42s
    8. Creating the sidebar form
      3m 23s
    9. Completing the sidebar
      3m 29s
    10. Making a table
      3m 12s
    11. Creating a footer
      2m 35s
  11. 1m 28s
    1. Goodbye
      1m 28s

Start learning today

Get unlimited access to all courses for just $25/month.

Become a member
Sometimes @lynda teaches me how to use a program and sometimes Lynda.com changes my life forever. @JosefShutter
@lynda lynda.com is an absolute life saver when it comes to learning todays software. Definitely recommend it! #higherlearning @Michael_Caraway
@lynda The best thing online! Your database of courses is great! To the mark and very helpful. Thanks! @ru22more
Got to create something yesterday I never thought I could do. #thanks @lynda @Ngventurella
I really do love @lynda as a learning platform. Never stop learning and developing, it’s probably our greatest gift as a species! @soundslikedavid
@lynda just subscribed to lynda.com all I can say its brilliant join now trust me @ButchSamurai
@lynda is an awesome resource. The membership is priceless if you take advantage of it. @diabetic_techie
One of the best decision I made this year. Buy a 1yr subscription to @lynda @cybercaptive
guys lynda.com (@lynda) is the best. So far I’ve learned Java, principles of OO programming, and now learning about MS project @lucasmitchell
Signed back up to @lynda dot com. I’ve missed it!! Proper geeking out right now! #timetolearn #geek @JayGodbold
Share a link to this course

What are exercise files?

Exercise files are the same files the author uses in the course. Save time by downloading the author's files instead of setting up your own files, and learn by following along with the instructor.

Can I take this course without the exercise files?

Yes! If you decide you would like the exercise files later, you can upgrade to a premium account any time.

Become a member Download sample files See plans and pricing

Please wait... please wait ...
Upgrade to get access to exercise files.

Exercise files video

How to use exercise files.

Learn by watching, listening, and doing, Exercise files are the same files the author uses in the course, so you can download them and follow along Premium memberships include access to all exercise files in the library.


Exercise files

Exercise files video

How to use exercise files.

For additional information on downloading and using exercise files, watch our instructional video or read the instructions in the FAQ .

This course includes free exercise files, so you can practice while you watch the course. To access all the exercise files in our library, become a Premium Member.

Join now Already a member? Log in

Are you sure you want to mark all the videos in this course as unwatched?

This will not affect your course history, your reports, or your certificates of completion for this course.


Mark all as unwatched Cancel

Congratulations

You have completed CSS Web Site Design.

Return to your organization's learning portal to continue training, or close this page.


OK
Become a member to add this course to a playlist

Join today and get unlimited access to the entire library of video courses—and create as many playlists as you like.

Get started

Already a member ?

Become a member to like this course.

Join today and get unlimited access to the entire library of video courses.

Get started

Already a member?

Exercise files

Learn by watching, listening, and doing! Exercise files are the same files the author uses in the course, so you can download them and follow along. Exercise files are available with all Premium memberships. Learn more

Get started

Already a Premium member?

Exercise files video

How to use exercise files.

Ask a question

Thanks for contacting us.
You’ll hear from our Customer Service team within 24 hours.

Please enter the text shown below:

The classic layout automatically defaults to the latest Flash Player.

To choose a different player, hold the cursor over your name at the top right of any lynda.com page and choose Site preferences from the dropdown menu.

Continue to classic layout Stay on new layout
Exercise files

Access exercise files from a button right under the course name.

Mark videos as unwatched

Remove icons showing you already watched videos if you want to start over.

Control your viewing experience

Make the video wide, narrow, full-screen, or pop the player out of the page into its own window.

Interactive transcripts

Click on text in the transcript to jump to that spot in the video. As the video plays, the relevant spot in the transcript will be highlighted.

Are you sure you want to delete this note?

No

Your file was successfully uploaded.

Thanks for signing up.

We’ll send you a confirmation email shortly.


Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

Keep up with news, tips, and latest courses with emails from lynda.com.

Sign up and receive emails about lynda.com and our online training library:

Here’s our privacy policy with more details about how we handle your information.

   
submit Lightbox submit clicked
Terms and conditions of use

We've updated our terms and conditions (now called terms of service).Go
Review and accept our updated terms of service.