Today is Fool’s Day and everyone is busy planning pranks on their colleagues and friends. However, more than that lot of big companies like Google, Opera and Yahoo among others play pranks on unsuspecting users who visit their websites.\
The folks over at Mozilla know this problem and have launched a new add-on for Firefox which will tell websites not to fool you. Once you have installed this Firefox add-on from here, you can visit the Advanced options and select the checkbox next to "Tell web sites I do not want to be fooled".
On checking this, Mozilla will pass a special header to websites which will tell them that you should not be fooled. Pretty neat extension from Mozilla. They have also written more about it on their blog, so you might want to head there to read about this extension.
P.S. If you fell for this, Mozilla pulled a fast one on you. Happy April Fool’s Day.