hide the webform after submission in webform 3.0
Do you want to allow users to submit it just once ?
If so have a look at node/123/webform/configure (where 123 is your form node id), there's a "Submission limit" option. If you choose "1" and "ever" then the form will be hidden with the following message: You have already submitted this form. View your previous submissions".

If you want to redirect your user to another page after submission, you can use the redirect option in the settings page.

Does this answer your question ? Can you elaborate it a little more if it doesn't answer it ?