XHTML browser
This Nokia browser guide just popped through the RSS aggregator.
There are as 1 billion GSM users (Source: GSM association), as opposed to at least 200 million Internet users (Source: Nielsen//Netratings).
Not every mobile user has an XHTML browser, but it’s probably growing quicker than PCs.
More specs, like the mimetype is quite useful to know what these devices can handle.