I have an image of a line that I want to appear under the text when I write a widget title. Right now the line is as a background image because I don't know how to format appropriately. see http://monsterbites365.com.

Help! Thanks!

First of all, underlining text that isn't a link is a very very bad idea. Very bad. Awful. Even if you think that underlining a header doesn't look like the rest of the links or something, don't do it. Pages use different link styles, and pretty much everyone has just got into the idea that "underline = link".

With that said, the CSS rule is 'text-decoration: underline'