htmlcsscss-expressions

CSS Expressions

I read somewhere that CSS Expressions were deprecated and shouldn't even be used. I had never heard of them and decided to take a look. I found a code example that kept a floating element in the same spot on the screen, even if you scrolled.

<html>
<style>
#fixed {
position:absolute;
left:10px;
top:expression(body.scrollTop + 50 + "px");
background:white;
border:1px solid red;}
</style>
<body>
<p id="fixed">Here is some text, which is fixed.</p>
<p>
[many times: "stuff <br/>"]
</p>
</body>
</html>

This reminded me of the sites that had the "share bars" and stuff at the bottom of their pages.

So...

  1. Is this how they are doing it?
  2. Is it alright to use Expressions in this situation?
  3. If not, what should I use?
  4. Are there any other interesting/helpful things that expressions can help with?
Solution

  • CSS expressions used to work in older IE's, but they have been completely abandoned in IE8:

    Dynamic properties (also called "CSS expressions") are no longer supported in Internet Explorer 8 and later, in IE8 Standards mode and higher. This decision was made for standards compliance, browser performance, and security reasons, as detailed in the IE blog entry titled Ending Expressions. Dynamic properties are still available in Internet Explorer 8 in either IE7 mode or IE5 mode.

    So it's arguably not really worth learning them any more.

    If not, what should I use?

    Depending on the use case, JavaScript or media queries.

    As @Yet Another Geek notes, your above example can be implemented using position: fixed. IE6 doesn't support that - the CSS expression was probably created to work around that.