WordPress MU

i have a problem while user active .

i got the first email and use the url to active ,
but the page show "Invalid activation key".

why ?????

i need answer

Copy and paste the URL into your browser -_-.

This is a great resource for asking for help:

http://codex.wordpress.org/Debugging_WPMU

Please also make sure you've also completed all of the steps in the readme file. Chances are you haven't.