So you're doing some clever Javascript and you have a link tag <a> tag that you want to act as say a tab or a button, but when you click down on the link you get this ugly dotted border highlighting your selection!

No good. Spice up your CSS with a little...
outline-style:none;
outline-width:0;
and you'll be living large with a more "tabular" or "buttonular" feel.

Or in 1 line.
a { outline: 0 none; }