SharePoint object model redirect to another page

Below is my requirement:

A user logs into a SharePoint application and clicks on some links(any link on the page) for the fi开发者_如何学Crst time. He should be redirected to a form in which a webpart with Submit button is placed. When submitted the form has to redirect to the clicked link (the page which he requested earlier). How do I pass this particular requested page url to the button submit.

There are plenty of ways to do this but the only watertight way is to use a feature to add a new masterpage which checks in the OnLoad if the user has accepted before or not and acts accordingly.

The other way is with javascript and model windows but it wont work on all browsers and will not be watertight.