Selectors like '.nav a' would not be allowed at all as a part of my team's CSS best practices, as it is a descendant selector that uses a tag as the key. (On the other hand, most sites, expecially non-dynamic sites, don't need to optimize CSS at all, as there are usually other things which are the bottleneck)
http://code.google.com/speed/page-speed/docs/rendering.html is a great page describing CSS performance.
Selectors like '.nav a' would not be allowed at all as a part of my team's CSS best practices, as it is a descendant selector that uses a tag as the key. (On the other hand, most sites, expecially non-dynamic sites, don't need to optimize CSS at all, as there are usually other things which are the bottleneck)