Now, check your internet speed, is it fast or slow, sometimes Facebook cant be opened from slow internet connection.
To check and diagnostic it, if you are using WIndows, press CTRL+ALT+delete, then a Task Manager will appear, then switch the tab to "Networking", there you go, you can see the internet speed.
Then, if it is fast, make sure your internet browser is supporting Javascript and Ajax format, Facebook has complicated webpage codes. So once again, make sure your internet browser supports them.
Example: Microsoft Internet Explorer and Mozilla Firefox, they are best internet browsers, and also upgrade them to the newer version.
If those ways not help you, check your browser configuration, make sure Javascript is marked to see the entire pages completedly.