What links are you talking about? Admin panel links or links on your website?
To modify look and feel of links in admin panel you need to edit file "manage/style.css" and remove "text-decoration:underline;" for "a:link" and "a:visited".
For your website links, you need to do the same but with your website css styles.
I am trying to add content with instant-update and it is permanently underlined when I hyperlink text to another page. I adjusted the CSS in the style.css but no change.