Updating url icon
Windows XP allows users to customize their color scheme, including toolbar backgrounds.You could get around this by making a square icon that doesn't have any transparent parts, but they don't look as interesting.Single color alpha channels, like GIF images, will have grainy-looking rounded exterior edges compared to a properly built alpha-blended icon, such as the ones on the Google Toolbar or Internet Explorer itself.One of the more interesting things a custom button can do is update its own button image and tooltip from a remote server at specific intervals. This allows a button to be used as a notification device, or as a status icon (for example, the weather, or whatever you can imagine).
A URL template like this could be used to make sure it had no effect on older toolbars: It should also be noted that any time an escape is used that is not recognized, the parser will substitute an empty string. Most icons that are used as favicons can also be used as custom button icons.
When clicked on, a search button can perform any of the following tasks: Custom Buttons).