Proxy Switcher Extension for firefox now supports PACs
https://add0n.com/proxy-switcher.html
Archive of posts tagged pac
Use proxy.pac with chrome & XFCE
gconftool-2 -R /system/http_proxy gconftool-2 -s /system/http_proxy/use_http_proxy -t bool true gconftool-2 -s /system/http_proxy/autoconfig_url -t string http://server.com/proxy.pac