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 and the css-discuss mailing list and wiki. There are plenty of other resources online as well.
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