This unique Mathematics based trick will probably work when websites are blocked based on the host name or their IP address.
The trick is to convert the human readable website address that's blocked (like facebook.com) into an IP address (188.8.131.52) and again translate this value to a decimal address which is probably not blocked by the website filters.
Related: How to Access Restricted Websites
Here's a step by step guide to render www.myspace.com to a decimal address:
Step 1: Get the IP address of a website by pinging the name (go the command prompt and type ping www.labnol.org to know the IP address of labnol.org)
Step 2: Open your PC's calculator, and change it to scientific mode (using the "View" menu)
Step 3: Enter each of the four IP octets, one by one, converting them to binary (enter number and click on the "Bin" radio button)
Thus 184.108.40.206 becomes
216 = 11011000 178 = 10110010 39 = 00100111 74 = 01001010
Notice how any binary numbers less than 8 digits long have had leading zeroes added to pad them out. Reassembled into IP address order, you get 11011000.10110010.00100111.01001010
Step 4: Remove the dots, so you get one huge line of binary, thus: 11011000101100100010011101001010
Step 5: Copy this binary string to clipboard, go to your scientific calculator, and hit the "Bin" button FIRST (as you are about to enter binary), THEN paste in the binary string.
Step 6: Click on the "Dec" button on your calculator, and you will get the converted value of 3635554122
Step 7: Add the http:// prefix and paste into your browser's address bar like http://3635554122
Wuntoo says - "I used to be in a place that had websense, where both website names and their corresponding IP addresses were blocked. However was able to get limited access by converting the IP address to decimal, which websense (at the time) did not know about. This might have changed since, or if your school runs an old version it might still work. Note that if you surf away from the page you might hit websense blocks again unless you manually reconstruct the next address you want to get to."