Conclusion
This is one of the few rules that addresses performance of the
page after it has been loaded, which is generally
when CSS expressions cause problems. However, in some cases, CSS
expressions can affect the load time of a page, too. One property at
Yahoo! had a CSS expression that caused a 20-second delay during the
initial rendering of the page. This result was unexpected and took a
while to diagnose. Similarly, who would have thought the CSS expression
used in the "Expression Counter" example would cause Internet Explorer
to lock up if the user clicked in a text field? A full discussion of
complicated CSS incompatibilities, such as min-width and position: fixed, is beyond the scope of this
book, and that's the pointâusing CSS expressions without a deep
understanding of the underlying implications is dangerous.
Avoid CSS expressions.
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