E-mail verification link

My codeigniter application has a user registration in place which is working fine. When a user registers he/she receives an e-mail with a link to verify / activate the user.

My problem is when e-mail verification is send to an outlook account, the user is able to click ou it and activate the account.

However, when the e-mail verification is send to gmail, upon clicking the link the users gets the following error.

"Redirect Notice

 The previous page is sending you to an invalid url (http:///prep.co.ke/auth/activate/60/82d57554e9e035d766cc6a0ae84a3d391392c730).

 If you do not want to visit that page, you can return to the previous page." 

What could be the problem?

Charles Ndunga