Along with the traditional single, thin-line underline style, you can opt for several different underlining varieties in Microsoft Word 2007.

Microsoft Word 2007's Track Changes feature does just that. When enabled, deleted text and changed text are displayed with a red line through the text.

I'd like to mimic the squiggly-red underlining that Word uses when there's a misspelling. The text-decoration property makes dotted underlines pretty easy, but not squiggly red like this, AFAICT ...

You can expand the usefulness of Word's Find and Replace functionality by using it to remove and/or apply specified formatting throughout a document.