Very simple add-on piece of CSS code to change the default fieldset CSS on vBulletin.
Paste the following line of code into the style you are using, this goes in the
Main CSS -> Additional CSS Definitions - making sure this is at the very end, just incase you are using a custom style.
HTML Code:
fieldset{border:1px solid #FF8200;padding:5px;-moz-border-radius:5px}
The
-moz-border-radius:5px part of this line cannot be rendered by Internet Explorer, it will work fine in Firefox, it will place curved corners on any occurance of the fieldset definition in vbulletin. The #FF8200 is just the color of the line used in the fieldset, in this example we have set this to orange.
How To Change The Fieldset CSS 
Linear Mode
