This add on works. However, it slows down my firefox 52.9 severely so that I cannot even load other tabs at the norm speed. Everything gets slowed down, including the tabs set for auto-refresh. Once I stop the auto-refresh, things get back to normal. Didn't see other people report this issue. Am I the only one having this issue? I am running Firefox 52.9 on Ubuntu 18.04LTS. I didn't want to upgrade to firefox quantum since certain add-ons are not available with the new firefox.