I am using the Atahualpa Theme and I think it’s annoying to get an outline around the header image while clicking on it by default. The outline is the dashed line around the header image that appears when you press your mouse button down while hovering over the image (at least in Firefox 3). There is a very easy way to remove it:

Add the following to your Appearance -> Athualpa Theme Options -> HTML/CSS inserts:

a:active, a:focus{outline: none}

Works for me :-)