Error after checkout

[speedstar]

after purchasing a product and checking out, hitting the "continue" button usually takes me back to the "home" page. But now I'm receiving an error now: "Page not found

The page you are looking for might have been removed,

had its name changed, or is temporarily unavailable."

 

 

Here is the my url: www.xxxxxxxx.com/notify%5B%5D?osCsid=c8de053351618f63a28910cc41acd23b

 

Where should I begin to trouble shoot??

 

the only thing I've done recently is get my index page: google verified. by adding a line of code within my index.html page. Not sure if this has anything to do with getting error??

 

please help. thx.