Sad fact of life: The same page that looks great in your browser sometimes looks weird -- or doesn't display at all -- in a different browser. Or in a different version of the same browser. Or in the same version of the same browser on a different computer.
You can avoid the problem by coding for different browsers or by sticking with HTML that's cross-browser compatible, but either way, you need to know what works in which browser.
Browser Sniffing
Netscape has a some good info and code here
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