Recently, I needed to create a dropdown menu using CSS. It was a pretty tricky menu since it contained convex and concave rounded corners and drop shadows. I wanted to do with a few images as possible and in a flexible way that display correctly regardless of font size, family or language. I used the CSS “border-imge” feature which worked great in modern browsers like Firefox and Chrome but IE 9 doesn’t support “border-image”. To accommodate IE users, I used Modernizr to detect whether a browser supported “border-image” or not and if not, display a different, simpler drop-down menu without fancy rounded corners. I think I’m going to have to add Modernizr to my toolset.
One caveat though is Modernizr depends on Javascript so if it’s disabled, Modernizr won’t be able to help you modernize your website.