Do you have Firebug for Firefox (press F12 to bring it up) or the Developer Tools (Ctrl-J) for Chrome? They make it trivial to toggle/edit CSS attributes on webpages.

In GWAN's case (using Firefox) the rule was:

p, h1, h2, h3, h4, ul, ol, legend, label { -moz-user-select: -moz-none; }