i think that requires of mod maybe to fix (Somesite has a mod for their google ads). It maybe in this part of the CSS script though.
Code:
.googleroot { padding:6px; line-height:130% }
.googlechild { padding:6px; margin-left:30px; line-height:130% }
.googlebottom, .googlebottom a:link, .googlebottom a:visited, .googlebottom a:active { font-size:11px; color: #3A4F6C; }
.googlish, .googlish a:link, .googlish a:visited, .googlish a:active { font-size:14px; font-weight:bold; color:#00D; }
.googlepagelinks { font-size:1.1em; letter-spacing:1px }
.googlesmall, .googlesmall a:link, .googlesmall a:active, .googlesmall a:visited { font-size:10px; color:#434951 }
I don't know though, i could be wrong about it.