The First Trick
Click your own profile, you'll see your own primary photo right there, right?
For Mozilla Firefox user, right-click on the picture and choose "Copy Image Location", open another Mozilla Firefox window or tab, and paste the photo URL on there.
Remove the numbers between slash "_" and ".jpg"
Then you'll see a little icon while the page is showing "404 - Page Not Found"
The Second Trick
Just same way with the previous trick, but you need click the primary photo and see it with large size by go to your "Profile Picture" album.
For Internet Explorer user, right-click on the picture and click "Properties", and see "Address (URL):" It show the address of the image, copy it and paste on another Internet Explorer window.
Copy the Image URL Address, and paste it on the another window or tab, remove the code from the second slash "_" from first to ".jpg", and put "/" after it.
Then you'll see a fan of Celtics. Just like the picture below...
Who is that, pal? By the way, where did he buy that scarf?
: Secret Facebook Favicon and Photo
: The First Trick Click your own profile, you'll see your own primary photo right there, right? For Mozilla Firefox user, right-click on t...