Do you happen to know why web browsers don't already do something like this? I find that a large number of domains are called every minute. I say domains as mos

Do you happen to know why web browsers don't already do something like this? I find that a large number of domains are called every minute. I say domains as most of them seem to be providing Javascript, although some of them are the web site I have loaded. Very occasionally I can see a legitimate purpose, such as refreshing a page showing a web interface to an email account, but most of the time there doesn't seem to be a legitimate purpose. Btw, this is from using Little Snitch on the Mac. If I temporarily block the refresh, nothing bad ever seems to happen.