This add-on does exactly what it claims: Gets rid of the annoying Yahoo banner ads AND recovers the space they consume! Ad Block Plus also gets rid of the ads, but leaves huge chunks of white space. This add-on moves and/or expands the actual mail frame up and over to make full use of the screen. No configuration neccessary, so it's extremely simple to use. Just install it, and forget it. No Restart needed either, which is nice. If you use Yahoo mail, this is a must-have add-on.