blocks|key|3176502|text|CSS表达式过去可以在旧的IE中使用，但它们已经被completely+abandoned+in+IE8:了|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3176503|在IE8标准模式和更高版本中，Internet+Explorer8和更高版本不再支持|3176504|动态属性(也称为"CSS表达式“)。此决定是出于符合标准、浏览器性能和安全原因而做出的，如标题为Ending+Expression的IE博客条目中所述。在Internet+Explorer8中，动态属性在IE7模式或IE5模式下仍然可用。|blockquote|3176505|3176506|3176507|因此，可以说不值得再学习它们了。|3176508|3176509|如果没有，我应该使用什么？|3176510|3176511|3176512|根据使用情形，可以选择JavaScript或media+queries。|3176513|正如@Yet+Another+Geek所说，上面的例子可以使用position:+fixed实现。IE6不支持这一点--+CSS表达式可能就是为了解决这个问题而创建的。|style|CODE|3176514|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/ms537634%2528v=vs.85%2529.aspx|1|http://www.smashingmagazine.com/2010/07/19/how-to-use-css3-media-queries-to-create-a-mobile-version-of-your-website/^0|P|S|0|0|0|0|0|0|0|0|0|0|0|M|D|1|0|V|F|0^^$0|@$1|2|3|4|5|6|7|17|8|@]|9|@$A|18|B|19|1|1A]]|C|$]]|$1|D|3|E|5|6|7|1B|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|1C|8|@]|9|@]|C|$]]|$1|I|3|-4|5|6|7|1D|8|@]|9|@]|C|$]]|$1|J|3|-4|5|6|7|1E|8|@]|9|@]|C|$]]|$1|K|3|L|5|6|7|1F|8|@]|9|@]|C|$]]|$1|M|3|-4|5|6|7|1G|8|@]|9|@]|C|$]]|$1|N|3|O|5|H|7|1H|8|@]|9|@]|C|$]]|$1|P|3|-4|5|6|7|1I|8|@]|9|@]|C|$]]|$1|Q|3|-4|5|6|7|1J|8|@]|9|@]|C|$]]|$1|R|3|S|5|6|7|1K|8|@]|9|@$A|1L|B|1M|1|1N]]|C|$]]|$1|T|3|U|5|6|7|1O|8|@$A|1P|B|1Q|V|W]]|9|@]|C|$]]|$1|X|3|-4|5|6|7|1R|8|@]|9|@]|C|$]]]|Y|$Z|$5|10|11|12|C|$13|14]]|15|$5|10|11|12|C|$13|16]]]]

CSS expressions used to work in older IE's, but they have been <a href="http://msdn.microsoft.com/en-us/library/ms537634%28v=vs.85%29.aspx" rel="noreferrer">completely abandoned in IE8:</a>

<blockquote>
 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.
</blockquote>

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

<blockquote>
 If not, what should I use?
</blockquote>

Depending on the use case, JavaScript or <a href="http://www.smashingmagazine.com/2010/07/19/how-to-use-css3-media-queries-to-create-a-mobile-version-of-your-website/" rel="noreferrer">media queries</a>.

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

blocks|key|268268|text|为了使元素在滚动时保持在同一位置，您应该使用position:fixed属性，然后使用top、bottom、left和right属性来确定它应该放置的位置。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|268269|编辑:下面是你的例子应该是什么样子：|268270|<html>
<style>
#fixed+{
position:fixed;
left:10px;
top:+50px;
background:white;
border:1px+solid+red;}
</style>
<body>
<p+id="fixed">Here+is+some+text,+which+is+fixed.

[many+times:+"stuff+ "]

</body>
</html>|code-block|syntax|javascript|268271|entityMap|0|LINK|mutability|MUTABLE|url|http://www.w3schools.com/Css/pr_class_position.asp^0|M|E|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@$A|T|B|U|1|V]]|C|$]]|$1|D|3|E|5|6|7|W|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|X|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]]]

For keeping an element in the same place while scrolling you should use the <a href="http://www.w3schools.com/Css/pr_class_position.asp" rel="noreferrer">position:fixed</a> property and then use top,bottom,left and right properties to tell where it should be positioned.

EDIT: Here how it should be for your example:

<pre><code>&lt;html&gt;
&lt;style&gt;
#fixed {
position:fixed;
left:10px;
top: 50px;
background:white;
border:1px solid red;}
&lt;/style&gt;
&lt;body&gt;
&lt;p id="fixed"&gt;Here is some text, which is fixed.&lt;/p&gt;
&lt;p&gt;
[many times: "stuff &lt;br/&gt;"]
&lt;/p&gt;
&lt;/body&gt;
&lt;/html&gt;
</code></pre>

blocks|key|2962833|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|2962834|可能不会。使用position:fixed或Javascript|ordered-list-item|offset|length|style|CODE|2962835|会更容易，除非你只支持IE+<+8。IE8%2B和其他浏览器不支持它*；它不符合标准，不会通过验证和使用|2962836|+position:fixed;+bottom:x;+top:y;+left:+a;+right:b;，其中x，y，a和b是偏移量。或者，除非你只使用旧版本的IE，否则不要使用Javascript|2962837|Again，。真的，倒了就好了。JS和普通CSS也可以达到同样的效果。|2962838|2962839|*无论如何，都是正式的。显然，它在@DalexL的Chrome上工作正常|2962840|entityMap^0|0|7|E|0|0|1|1E|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|S|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|T|7|@$D|U|E|V|F|G]]|8|@]|9|$]]|$1|H|3|I|4|C|6|W|7|@]|8|@]|9|$]]|$1|J|3|K|4|C|6|X|7|@$D|Y|E|Z|F|G]]|8|@]|9|$]]|$1|L|3|M|4|C|6|10|7|@]|8|@]|9|$]]|$1|N|3|-4|4|5|6|11|7|@]|8|@]|9|$]]|$1|O|3|P|4|5|6|12|7|@]|8|@]|9|$]]|$1|Q|3|-4|4|5|6|13|7|@]|8|@]|9|$]]]|R|$]]

<ol>
<li>Probably not. It's easier to use <code>position:fixed</code> or Javascript</li>
<li>Not unless you're only supporting IE &lt; 8. IE8+ and other browsers don't support it*; it's not standards compliant and won't pass validation</li>
<li>Use <code>position:fixed; bottom:x; top:y; left: a; right:b;</code> where x, y, a, and b are offsets. Or, use Javascript</li>
<li>Again, not unless you're using old versions of IE only. Really, just dump it. the same effects can be achieved with JS and normal CSS. </li>
</ol>

*Officially, anyways. Apparently it worked on Chrome for @DalexL

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.

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

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

So...

<ol>
<li>Is this how they are doing it?</li>
<li>Is it alright to use Expressions in this situation?</li>
<li>If not, what should I use?</li>
<li>Are there any other interesting/helpful things that expressions can help with?</li>
</ol>

CSS Expressions

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我在某处读到CSS表达式已被弃用，甚至不应该使用。我从来没有听说过他们，所以我决定去看看。我发现了一个代码示例，它将一个浮动元素保留在屏幕上的同一位置，即使您滚动。<html><style>#fixed {position:absolute;left:10px;top:expression(body.scrollTop...

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