Set the Time for Browsing a Site

When you are browsing the internet, and you want to spend some time say for example 15-20 minutes, for fun before you get into serious work.
What you do in this case? Either you watch the time or you set a stop watch.
Here is a simple way to do this, Time Tracker Addon by Firefox.
 
                                         
Some of the features of this addons are:
- Tracks browsing time across sessions
- Pauses automatically when you stop browsing
- Reset counter
- Pause toggle per window
- List 'work' sites that should not count
- Tool tip showing total time today, since last reset and since installing.

Now you can surf the internet for the desired time, how much that you want.