If you have ever used Top Cashback and have LassPass as your password manager, you may find that you can never auto login to the site, it just keeps going in a loop. I found a fix on the LassPass forum.
What you need to do is edit the saved Topcashback entry in LassPass. Then click on Edit Form Fields and then remove every item except for the top two which are you username and password. Use the small blue _ to remove each entry. The form should just have the two fields left. Now click save and try and log into TopCashback now and should work fine.
If you would like to sign up for LastPass, please use this link.