[CannonFodder]

Login to your admin panel.
Scroll down on the left menu to templates. Find the template set you want to edit, click show all.

Open the template called "headinclude"

Find

PHP Code:

A:link, A:visited, A:active {
    COLOR: {linkcolor}; 


Underneath it add

PHP Code:

    TEXT-DECORATION: none; 


Next, find

PHP Code:

A:hover {
    COLOR: {hovercolor}; 


underneath it add

PHP Code:

    TEXT-DECORATION: underline; 


Hope that helps!