Majority of the social networking accounts are blocked in corporate offices, schools, workplace and educational institutions. In such cases, you have to look for workarounds to open Facebook. There are many other options but the quickest and easiest way is to use the web version of opera mini browser to open Facebook . Just open the Opera mini demo link in your browser and you can open Facebook homepage.
Opera mini is meant to surf the web from mobile phones and it is a great way to access blocked websites. You can access the mobile version of Facebook from http://m.facebook.com.