Devthought had a little CSS tip the other day that is definitely worth repeating. It's not new, it's just an important little trick to know.

And here it is:

img { -ms-interpolation-mode: bicubic; }

If you use width or height tags to resize images in your markup, IE will ensure they look incredibly awful unless you use this little snippet. In general, resizing images in the browser isn't recommended, but of course there are always exceptions.