IE7 acronym underline in a fieldset legend

I have an acronym inside of a fieldset/legend:

<fieldset>
    <legend>
        <acronym>foo</acronym>
    </legend>
</fieldset>

In Firefox this gets rendered with a dotted underline to signal the user that there is something there if they mouseover it.

In IE the dotted un开发者_JAVA百科derline doesn't show up?

I tried forcing it in css like this:

style="border-bottom:1px dotted #000000 !important;"

But I can't seem to get it to show up. Any ideas?

Set the acronym's display style to inline-block That will let IE7 show the border you specify in the style.