A nifty tool that’s quite useful in catching errors in your PAC [proxy auto config] file is “pacparser”. You can find it here:
http://code.google.com/p/pacparser/
The win32 zip file contains a binary executable that you just point to your PAC file and an example URL to test with. It will then use javascript to parse the file and display where it got stuck or if successful, the results returned.
When encountering an error, it also highlights in which line the error was encountered, leading to easier troubleshooting.
FYI: a pac file is a setting in your browser that instructs the browser which proxy to use. It’s useful for cases where you’d only want to use a proxy conditionally (example only certain site go through proxy A, the rest through proxy B), proxy load balancing and failover, etc
http://en.wikipedia.org/wiki/Proxy_auto-config
Quite a good PAC file checker.
David Vassallo's Blog 