This syntax isn’t supported in many browsers, so the specification calls on
browser vendors to support both the single- and double-colon syntax.You can use content in other ways, too. For example, you might use it to add
visual labels to text. One common use for this is to employ content to put the
words “external link” next to URLs that link out to other sites. You have to
be careful not to cross the line from design to content. The CSS content prop-
erty should be used for design-related things only, not for injecting actual
page content.We’ve covered how to make a web page look different when it’s sent to a
printer, but now let’s see how to change the page content’s appearance based
on the screen size.Chapter 4. Styling Content and Interfaces • 80
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