Chain both class selectors (without a space in between):
.foo.bar {
/* Styles for element(s) with foo AND bar classes */
}
If you still have to deal with ancient browsers like Internet Explorer 6, be aware that it doesn't read chained class selectors correctly: it'll only read the last class selector (.bar in this case) instead, regardless of what other classes you list.
To illustrate how other browsers and IE6 interpret this, consider this snippet:
* {
color: black;
}
.foo.bar {
color: red;
}
<div class="foo">1. Hello Foo</div>
<div class="foo bar">2. Hello World</div>
<div class="bar">3. Hello Bar</div>
The page will look like this:
On supported browsers:
- Not selected as this element only has class
foo.
- Selected as this element has both classes
foo and bar.
- Not selected as this element only has class
bar.
In Internet Explorer 6:
- Not selected as this element doesn't have class
bar.
- Selected as this element has class
bar, regardless of any other classes listed.
- Selected as this element has class
bar.