Design Some Themes

Writing CSS rules for elements such as section and p is great, but what if you want to make some of them look different from others? On this card you will learn how to apply different sets of style rules to elements of the same type and create a different theme for each page on your website!

Go to your style sheet file and add the following — be sure to include the dot in front!

.topDivider {
  border-top-style: solid;
  border-top-width: 2px;
  border-top-color: #F5FFFA;
  padding-bottom: 10px;
}

Now go to birds.html (or the HTML file you’re working on if you’re using your own project), and add the following attribute to each section tag:

<section class="topDivider">

You should see a line appear above each section on the page. Congratulations — you’ve just used your first CSS class!

Page with lines in between the sections

Look at how your web page looks now and compare it to the other pages that have section elements. You’ll see that only the ones where you added the attribute class="topDivider" will have the line on top.

How does it work?

Remember that when you use a CSS selector such as section or p or nav ul, the style rules apply to all the elements of that type on your website.

With CSS classes, you’re able to change the style of just some of the elements.

Putting a dot in front of your selector makes it into a class selector. A class can have any name, so it doesn’t have to be the name of a HTML element. For example:

.myAwesomeClass {
  /* my cool style rules go here */
}

To choose which elements the style rules apply to, you add the class attribute to those elements in the HTML code: put the name of the class in as the value for the attribute, without the dot, like this:

class="myAwesomeClass"

Ready to try another class? Add the following CSS code to styles.css:

.stylishBox {
  background-color: #87CEFA;
  color: #A52A2A;
  border-style: solid;
  border-width: 2px;
  border-color: #F5FFFA;
  border-radius: 10px;
}

Then, on a different page of your website, add the class to some elements there. I’m going to add it to the section elements on the Conservation page of my website, like this: <section class="stylishBox">.

It looks great, but now my sections are all squashed together.

Nice looking sections squashed together

You can apply as many CSS classes to an element as you like. Just write the names of all the classes you want to use inside the class attribute (remember, without the dot!), separating them with spaces.

Let’s make another CSS class to give the sections some margin and padding. In the styles.css file, create the following CSS class:

.someSpacing {
  padding: 10px;
  margin-top: 20px;
}

In your html code, add the new class to each of the elements you were working on, like this:

<section class="stylishBox someSpacing">

Sections with margin and padding added

So CSS classes let you choose which elements to style, and they let you reuse the same set of style rules on any elements you want.

Go to index.html and add the stylishBox class to the main element, or another element on the page. You can remove it again afterwards!

<main class="stylishBox">

Here’s what my home page looks like with the CSS class. I’ve also added the topDivider and someSpacing classes to the img tag with the picture of the barn owl.

CSS classes being used on the home page

Challenge: make some new classes

Use CSS classes to define a few different picture sizes for your website, for example .smallPictures and .mediumPictures. Then remove the width attribute from each of your img elements and add the appropriate class instead.

I need a hint

You can make a CSS class that defines just the width of an element like this:

.smallPictures {
  width: 100px;
}

Here’s an img tag with a width attribute:

<img src="barn-owl.jpg" alt="A barn owl" width="100px" />

When you remove the width attribute and control the size with the CSS class instead, it looks like this:

<img src="barn-owl.jpg" class="smallPictures" alt="A barn owl" />

By using a CSS class, you can easily change the width of all the pictures at once by changing only one line of code in your style sheet!

Bird Watch Website 2.0