Popular Web sites are the bane of any would-be productive day's existence and, fortunately, there are ways to help.
If willpower isn't your thing, there are lots of programs out there that can block access to Web sites. The problem with a lot of these programs is that you have to manually disable the block--if your conviction really falters your can still unblock it before your work gets done.
FocalFilter is a program for Windows operating systems that can block a user-generated list of Web sites for a specified period of time. The lock on these sites will persist until the time as elapsed, at which point you can extend the lock or unblock them.

Step 1: Download and install FocalFilter.
Step 2: Open the Windows start menu and type FocalFilter into the search box. Run the FocalFilter program the appears in the list.
Step 3: Click the Edit My Site List to open a new window containing the sites to be blocked. Add sites that you want blocked, one on each line. Click the Save button when finished.
Step 4: Click on the area next to the label Block for. A list of available times, ranging from 5 minutes to 12 hours, will be displayed. Select the time the best fits your needs.
Step 5: Click the Block My Site List button to block your browsers from visiting your list of Web sites. Note that you might have to restart your browser before the block will work.
The nice thing about this program is that the blocks are completely temporary. You can use other programs to block access to websites that you or anyone else who uses your computer never want to visit, and not have to worry about accidentally disabling those blocks when unblocking your favorite site.