CSS - .id:hover a:before items jumping around

[kepler001]

I have a list a horizontal list of 3 with a:before and a:hover. Upon hovering the element jumps around a little before it settles in it's position. Tried 3 popular browsers. Any ideas for a fix?\[code\].twitter a:before{content: url(.jpg);padding-right: 10px;position: relative;bottom: -.4em;}.twitter:hover a:before {content: url(.jpg);padding-right: 10px;position: relative;bottom: -.4em;}\[/code\]http://nobodyfilm.org - middle section twitter - facebook - trailer buttons. It only happens the first time you load the site if I'm not mistaken.