|"Can a virus get through my firewall?"|
Yes. A firewall only protects unauthorized access through a network while allowing authorized access (see further description below). If you visit a page encrypted with a virus or other malware, it won't stop you. Always have a virus/malware scanner active and up-to-date. If you're running a scan, disconnect the machine from the internet (to keep more "nasties" from getting into your machine).
"Channeling the spirit of jboy..."