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Writing a selector

From: CSS: Core Concepts

Video: Writing a selector

The first thing we'll do when writing CSS is to explore writing a selector, and how it can help us target elements on the page. Now, a little bit later on, we're going to explore the different types of selectors in more detail. For right now, let's just concentrate on what a selector is and what it allows us to do. So I'm going to go over to my exercise files, go in the 01_04 folder, and open up selector.htm. So I want to just briefly go over the structure of the document with you.

Writing a selector

The first thing we'll do when writing CSS is to explore writing a selector, and how it can help us target elements on the page. Now, a little bit later on, we're going to explore the different types of selectors in more detail. For right now, let's just concentrate on what a selector is and what it allows us to do. So I'm going to go over to my exercise files, go in the 01_04 folder, and open up selector.htm. So I want to just briefly go over the structure of the document with you.

You're going to notice right off the bat that inside of the head of the document we have the style tag. You know we're going to go over embedded styles in more detail a little bit later on, but for now, the style tag allows us to write CSS directly within this document. In the body of our document we can see that we have a h1, below that we have a paragraph, and then we have a div tag in which a h2 and a paragraph are both located, so those are the elements on the page that we're going need to be targeting. We also have a sample rule already written for us. All it needs is a selector, and that is what we're going to go ahead and write right now.

So I'm just going to place my cursor right before the opening curly brace of our CSS rule, and I'm going to type in P. That is a very simple element selector, and it's going to target all the paragraphs on the page. So I'm going to save the page, and I'm going to preview that in a browser. Now depending upon which authoring tool you're using, you're probably going to have different methods for previewing within the browser. Some of them you are actually going to have to go out to the browser and open the file separately; others such as Aptana Studio and Dreamweaver, they give you an option of previewing from the browser directly within the application.

In Aptana, all I do is go right up here to this little Play button and I can grab the pulldown menu and I can run from any browser that I've configured. So I'm going to go ahead and run this from Chrome, and now I can see that all of the paragraphs on the page, because of the element selector that we just wrote, are now red. So I want to jump back into Aptana Studio, and I'm just going to change the selector. So instead of the just having a paragraph selector, I'm going to type in div, and then a space, so now div p. This is what's known as a descendent selector, and it's only going to target paragraphs that are found within a div.

So I'm going to go ahead and save this, go back out to Chrome, refresh the page, and you can see that now instead of targeting every single paragraph on the page, we've filtered it a little bit, and we're only targeting the paragraph that's inside of the div tag itself. So I want to go back into our editor, and we'll make one more change to our selector. I'm just going to go right after the div p, type in a comma, and then h1. Now, this is what's known as a group selector, and what it is doing is it's going to target both of these. It'll target all paragraphs inside of a div tag, as well as all h1s on the page.

So again, I'm going to save that, go back to Chrome, refresh the page, and now you can see that now in addition to targeting this paragraph, it's also targeting the heading 1 up here as well. Now we're going to learn more about those selector types, and as we do that, you're going to become a lot more comfortable targeting specific page elements. Now the real challenge for you as an author is to make sure that you're writing the most efficient selectors that you can. The more complex the selector gets, the more work to browser has to do in order to render it properly. By having a thorough understanding of all the different types of selectors and when they're appropriate to use, you'll be a lot better prepared when planning and executing your styles.

Now although we are going to be examining selector types in more detail later, I want to mention a very, very helpful resource. And I'm just going to click over here on my tabs, because I already have this pre-loaded up here. This is the Selectors Level 3 module from the W3C. Now this is the specification that describes selectors in more detail. However, if you scroll down to the Selectors section--and I'm just going to do that as quickly as possible here; here we go-- you get a list of all of the different selector types, and it gives you a nice quick overview of the selector and what it targets.

Now as you're learning selectors a little bit later on, I would recommend actually having this and referring back to it, because it's an extremely handy resource to have on hand.

Show transcript

This video is part of

Image for CSS: Core Concepts
CSS: Core Concepts

81 video lessons · 40915 viewers

James Williamson
Author

 
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  1. 4m 57s
    1. Welcome
      55s
    2. Using the exercise files
      4m 2s
  2. 1h 7m
    1. Exploring default styling
      4m 56s
    2. CSS authoring tools
      2m 29s
    3. CSS syntax
      4m 45s
    4. Writing a selector
      4m 10s
    5. Setting properties
      8m 40s
    6. Common units of measurement
      7m 47s
    7. Inline styles
      5m 1s
    8. Embedded styles
      5m 19s
    9. Using external style sheets
      10m 34s
    10. Checking for browser support
      8m 48s
    11. Dealing with browser inconsistencies
      5m 30s
  3. 2h 15m
    1. Structuring HTML correctly
      2m 51s
    2. Element selectors
      4m 52s
    3. Class selectors
      6m 4s
    4. ID selectors
      3m 27s
    5. Using classes and IDs
      10m 7s
    6. Element-specific selectors
      4m 35s
    7. The universal selector
      5m 42s
    8. Grouping selectors
      4m 49s
    9. Descendent selectors
      7m 32s
    10. Child selectors
      5m 7s
    11. Adjacent selectors
      5m 30s
    12. Attribute selectors
      12m 43s
    13. Pseudo-class selectors
      3m 54s
    14. Dynamic pseudo-class selectors
      8m 29s
    15. Structural pseudo-class selectors
      6m 45s
    16. Nth-child selectors
      13m 10s
    17. Pseudo-element selectors
      12m 40s
    18. Targeting page content: Lab
      8m 56s
    19. Targeting page content: Solution
      7m 59s
  4. 42m 39s
    1. What happens when styles conflict?
      4m 0s
    2. Understanding the cascade
      5m 47s
    3. Using inheritance
      6m 11s
    4. Selector specificity
      6m 55s
    5. The !important declaration
      4m 5s
    6. Reducing conflicts through planning
      3m 33s
    7. Resolving conflicts: Lab
      6m 45s
    8. Resolving conflicts: Solution
      5m 23s
  5. 1h 47m
    1. Setting a font family
      7m 10s
    2. Using @font-face
      9m 18s
    3. Setting font size
      7m 35s
    4. Font style and font weight
      6m 52s
    5. Transforming text
      3m 58s
    6. Using text variants
      2m 49s
    7. Text decoration options
      4m 26s
    8. Setting text color
      3m 2s
    9. Writing font shorthand notation
      8m 49s
    10. Controlling text alignment
      6m 33s
    11. Letter and word spacing
      9m 11s
    12. Indenting text
      4m 30s
    13. Adjusting paragraph line height
      10m 30s
    14. Controlling the space between elements
      6m 41s
    15. Basic text formatting: Lab
      8m 45s
    16. Basic text formatting: Solution
      7m 14s
  6. 2h 1m
    1. Understanding the box model
      16m 53s
    2. Controlling element spacing
      14m 29s
    3. Controlling interior spacing
      10m 49s
    4. Margin and padding shorthand notation
      6m 27s
    5. Adding borders
      8m 57s
    6. Defining element size
      10m 7s
    7. Creating rounded corners
      6m 58s
    8. Background properties
      2m 51s
    9. Using background images
      5m 10s
    10. Controlling image positioning
      10m 25s
    11. Using multiple backgrounds
      7m 5s
    12. Background shorthand notation
      5m 25s
    13. Styling container elements: Lab
      7m 55s
    14. Styling container elements: Solution
      8m 17s
  7. 47m 51s
    1. Color keyword definitions
      5m 4s
    2. Understanding hexadecimal notation
      6m 5s
    3. Using RGB values
      4m 58s
    4. Using HSL values
      5m 17s
    5. Working with opacity
      2m 23s
    6. Using RGBa and HSLa
      3m 8s
    7. Styling drop shadows
      5m 38s
    8. CSS gradients
      6m 32s
    9. Working with color: Lab
      4m 26s
    10. Working with color: Solution
      4m 20s
  8. 1m 58s
    1. Additional resources
      1m 58s

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