what works in IE+Netscape both, and what doesn't?

ok im a young computer junkie, i've made tons of good looking IE sites, and have been totally ignoring netscape. but now i've been urged to enter into a local designers contest and it would be usefull to know what works in both IE and Netscape browsers.

Anything pertaining to
-ssi
-css
-layers
-forms

in both IE and Netscape would be helpful.

thx
-evann

ps otherwise im going to have to guess and check every minor detail

You're going to have to check every minor detail. Even if you avoid the browser-specific tags, each browser implements the "standard" stuff differently. For instance, the default cellspacing and cellpadding for tables are different in IE than they are in Navigator. Same goes for the default "padding"/"margin" for HTML pages. IE also displays pages based upon 96 dpi, whereas Netscape (4.x) uses 72 dpi, so that will throw off any calculated dimensions.