There is now an updated version of the Cashback Guardian for Firefox users, version 0.1.9 now includes the ability to tell it to stop letting you know about cashback offers for certain websites. For example if you always get told about offers when you visit your online banking site, or Yahoo and you'd rather not, simply click the 'Ignore Site Offers'* button and you shall see them no more.
Mozilla have also finally removed the experimental status from the Cashback Guardian, which means it should now work with the automatic update notifications in Firefox. If you've not upgraded yet, or you've yet to try Cashback Guardian why not check it out here, don't forget to add a review if you find the add-on useful and be sure to let your friends know.
*Please note, this feature is not yet available for the Internet Explore version of Cashback Guardian.