Opera 10.53, Apple Safari 4, Google Chrome 4, Mozilla Firefox 3.0 and above are fully supported by this service. Microsoft Internet Explorer is not fully supported for it uses a different kind of plugins update check.
To check a supported browser for the plugins, just navigate your browser to the following address : http://www.mozilla.com/en-US/plugincheck/. The process requires that you have JavaScipt enabled in your browser.
Here is the result of extensions update check in Google Chrome 4 running under Windows Vista. It found one outdatd extension :
Here is the result of plugins update check in Microsoft Internet Explorer 8 running under Windows Vista. It clearly states that support for this browser is limited.
Here is the result of plugins update check in Opera 10.53 running under Windows Vista. It finds not only the outdated plugin, but also tells that an updated version of Opera browser is available. Now, this is impressing.