It appears that {http|ftp}://gentoo.chem.wisc.edu/gentoo has been removed from the download mirror list. It was probably caused by a recent permissions flap and we are in the process of resolving the cause of that. Mirror is hosted by University of Wisconsin at Madison Department of Chemistry. Please add us back
The problem has been resolved.
The cause of overly liberal permissions has been resolved.
Yes, that was the reason we were forced to take you off the page. I've re-added you now. Please ensure this doesn't happen in the future. It does mess up things when one mirror puts out release ISOs before the rest of them do. Thanks!