Inline style to act as :hover in CSS
If you are only debugging, you might use javascript to modify the css:
<a onmouseover="this.style.textDecoration='underline';"
onmouseout="this.style.textDecoration='none';">bar</a>
I'm afraid it can't be done, the pseudo-class selectors can't be set in-line, you'll have to do it on the page or on a stylesheet.
I should mention that technically you should be able to do it according to the CSS spec, but most browsers don't support it
Edit: I just did a quick test with this:
<a href="test.html" style="{color: blue; background: white}
:visited {color: green}
:hover {background: yellow}
:visited:hover {color: purple}">Test</a>
And it doesn't work in IE7, IE8 beta 2, Firefox or Chrome. Can anyone else test in any other browsers?