In scenarios where you are trying to block an entire website, a whole subdomain or network zone( like www.facebook.com ), you might think of Windows hosts file or COMODO firewall first, however you can’t use them to block a specific/particular URL like twitter.com/diggfreeware. But if you are a Chrome user, the things become easier.
SiteBlock is a Chrome extension developed by csapuntz, it provides you the ability to block as many URLs as you want, using SiteBlock is easy, just enter the URLs in the list, one per line, and press the “save options” button, then when you open a blocked site, the content of the website will not be loaded. SiteBlock also supports working in incognito mode.
On the other hand, SiteBlock supports blocking all websites except those in the white list.
SiteBlock is available at Google.
Chrome Nanny is another Google Chrome extension which is similar to SiteBlock, but it’s more complicated, it allows to define a rule for each URL, and supports regular expression( wildcard ), period definition, statistics plotting, and allows to close tab / redirect to another URL / show “Site blocked” page when a site is blocked.