changing URl parameter values

What is the best practise to do when user change the values of URL parameter?

• Redirect to login page.
• sho开发者_如何学编程w error page with page is no exist message.
• still in the same page.

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1. Your URL should be defined that way that it always points to a resource.
2. There might be additional parts of the URL that are used to refine the resource (such as paging index or something else necessary only for that resource).
3. If a resource can be found - let the resource handle the wrong URL.
4. If the resource is not allowed to be accessed by the user -> login screen.
5. If no resource -> error.
6. no further case specified.