Assuming that your PC doesn't have any malicious coin mining program installed there are few options to block coin mining while you are browsing a particular website. (techhundred.com)
There are more advanced mining programs but they often require users to be acquainted with the command line so we won't cover them here. (cryptojunky.com)
GUI miner is a basic Bitcoin mining program that also works well for beginners. (cryptojunky.com)