This is fairly typical which is why you have to be prepared to do cross-browser development: in other words
detect[
^] the client browser and adjust your CSS to suit: there are many examples here and on Google; e.g. the
box model hack[
^]. It is also worth remembering that different versions of a browser may also render your content in strange and frustrating ways; IE6, for instance, is different from IE7, IE8 and certainly IE9.
As far as color goes look up
web safe colors[
^] as a start.
That should get you going and bear in mind that this is not an Asp.Net problem it is a browser issue that can be dealt with by employing good research and careful design.