You should make sure, in particular, that your email address is up to date. You can change any fields in your profile, except for your username. Information about the various options that you have in your profile are available on this page . When you make modifications to your posts, a note will appear at the bottom of the post telling other users that you have edited your post. Moderators and administrators can also edit your messages.
Signatures are only available to registered users.
You can specify in your profile a signature to use at the bottom of your posts. When you post, there is an option to use your signature. If you want to turn the signature off in the future, you can come back and edit your post. If you have specified a signature in your profile, the box will be automatically ticked for you. You can search any forum that you have permission to search - you will not be allowed to search through private forums unless the administrator has given your the necessary security rights to do so.