My browser is not supported anymore, how do I fix that?

Which browser are you using? The built in one? You may be able to install another browser in the Play Store which is compatible with more modern websites.

You may also be able to get around app restrictions by side loading a newer version of the browser than your tablet would normally support. But legitimate copies of those can also be difficult to find and many sites which allow you to download .apk (android app) files are pretty shady or will load the tablet up with junk ware.