Danny reported about Yahoo's new robots-nocontent attribute, which allows you to tell Yahoo's relevancy algorithms to ignore noisy parts of your pages:
The new robots-nocontent tag now allows you to tell Yahoo to ignore the clutter. Simply use the tag (technically, it's an attribute) to surround text you do NOT want included in searchable content within Yahoo.
How? It's a little complicated, but not too hard. You need to have a class attribute called robots-nocontent assigned to some tag within your document. The attribute looks like this: