While Google and many companies celebrate this day with harmless pranks, many malicious attacks have also occurred in the past.  Please be careful with email, websites, and even what you read on this day.

http://aprilfoolsdayontheweb.com/

http://www.esecurityplanet.com/trends/article.php/3929681/Dont-be-Fooled-on-April-Fools-Day.htm