Notes about the HDML file extension:
Incorrect file associations could be the result of underlying issues within your PC system. As such it is highly recommended to scan your PC for invalid registry entries, unused processes and other unfavourable system settings to identify slowdown issues.
The HDML file type is primarily associated with 'Handheld Markup Language File'. In 1997, a company called Unwired Planet invented HDML and the browser that reads it, called the UP.Browser. At the time, it was the great hope of the so-called "third-generation," Web-enabled browser. But a lack of support on both ends left HDML temporarily high and dry. Recently, though, the WAP Forum, founded by Unwired Planet (since evolved into Phone.com and most recently Openwave) and such industry movers as Nokia and Motorola, unveiled WAP, the wireless application protocol, which in conjunction with this year's smaller, cheaper phones with greater screen real estate allows much more robust and widespread phone surfing.