Userbars are small rectangular images that are designed to be put in an Internet forum signature block. Userbars may be animated if the artist wishes. They are often used to show the user's interests, hobbies, or graphical skills. Userbar standards are often strictly defined and enforced by communities to ensure that they all have a neat appearance when animated or when stacked vertically. Although there is some variation, most are not wider than 350 pixels and not higher than 19 pixels so they can fit in with other userbars. Many userbars are as little as 1kb. Some may be larger depending on animation size.