Hi, I succesfully jailbroke my itouch using greenpois0n but when I connect the itouch to my pc itunes opens and it says it has an update but is it safe to do?
Nooooo! If you update, iTunes keeps all your data (none of the Cydia stuff though) and deletes everything else and then loads a new firmware onto it. If you update your firmware you WILL break your jailbreak and you won't be able downgrade unless you've got your shsh saved. Which I assume you don't. Just think of this as a general rule, unless you don't want your jailbreak don't upgrade!
Every time there's an iTunes update, just check the mmi news category and within a week at the most one of the guys would have tested if it was jailbreak safe and all that