Gravatars are “Globally Recognized Avatars” and were developed by the folks responsible for Word Press. It works as a third party provider of avatars that allows you to use the same avatar on multiple sites. Because the avatars are useful to help distinguish between members more easily a unique avatar is generated and displayed for users who don’t have a custom avatar with gravatar.com.
To begin using a custom avatar, just go to http://en.gravatar.com/ and upload an image for the email address you use on able2know and it will appear within a few hours.
Note: They cache their images and any changes may take between minutes or hours to show up on their end, but if you still don’t see an avatar change after a day then you may have the old avatar in your browser cache and clearing your browser cache should solve it.