Dave, Firefox is rendering the border you've defined on the input selector. Use inline CSS of border:0; or give it a class/ID (as you have the other form elements) and add a rule to your stylesheet to stop this from appearing.
I remember this bug from Mozilla a long time ago. I did this:
input[type=hidden] { display: none !important; // or whatever rules you need to override } /AndersN ****************************************************** The discussion list for http://webstandardsgroup.org/ See http://webstandardsgroup.org/mail/guidelines.cfm for some hints on posting to the list & getting help ******************************************************