There is only one file type that uses the .M2S extension:
Maxthon 2 Browser Skin File
Theme or skin for the Maxthon 2 Web browser; used to customize the look and feel of the Maxthon browser interface; includes the default settings for the skin and references to images used by the skin.
M2S files support .PNG images, which allows buttons and icons referenced by the skin to use different levels of transparency.
Updated: April 25, 2008