You probably haven't heard people talking about this on on the Ruby on Rails mailing list because these are not Ruby on Rails-specific issues. It sounds like you should take some time to study up on these areas. Though they're getting a bit old, I recommend Jeffrey Zeldman's "Designing with Web Standards" and Eric Meyer's "Eric Meyer on CSS".
Online references include A List Apart[1] and the css-discuss mailing list and wiki[2]. There are plenty of other resources online as well.
Michael Glaesemann
grzm seespotcode net
And the links I intended to include:
[1](http://www.alistapart.com/)
[2](http://css-discuss.incutio.com/)
Michael Glaesemann
grzm seespotcode net
Actually I have found IE7 to be my worst problem. Most CSS hacks have
been well explored on IE6 and IE5, but
IE7 includes a whole lot more incompatibilities. I have spent more
time on futzing with CSS to get it to work on IE7, than it took me to
write the rails app in the first place!
I even started using tables for layout again (I know gasp!!), because
IE7 broke all my nice CSS formatting.
The biggest problem which I never solved was a nice thumbnail layout
using CSS which worked on everything but IE7, on IE7 the thumbnails
were no longer clickable. That was the last straw that took me back to
using a table.
This is the gallery CSS as you can see works great except on IE7 you
can't click the thumbails!
http://accessat.c-net.us/test/gallery2.html
Just one example of the pain I have been through! Why can't everyone
use Firefox 
be sure you aren't allowing IE to operate in quirks mode (see
CSS - Quirks mode and strict mode for a discussion)
set doctype
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
-Ryan