resize the content property’s image

I’ve run into the same problem before. Try this:

#geog:before
{
    display: inline-block;
    width: 16px;
    height: 16px;
    margin-right: 5px;
    content: "";
    background: url("icons/geogebra.ico") no-repeat 0 0;
    background-size: 100%;
}

I’m sure you’ll have to tweak those values, but that worked for me. Of course, this won’t work if you can’t set it as a background image for some reason. Best of luck to you!