A DOTHTML file is a Microsoft Word template document saved in HTML version. It can be opened in web browser and contents are displayed as any other web page. DOTHTML files are generated from Microsoft Word .DOT files that contain pre-formatted settings for generating these files. When a DOT file is converted to DOCHTML, all these settings are retained and the converted DOTHTML file is displayed with similar formatting as the original DOT file. This way, published templates can be viewed in web browser.
DOTHTML File Format - More Information
DOTHTML files are saved as HTML files and contain HTML source code that can be opened with any HTML editor. In the initial days, Microsoft Word offered the HTML versions of all of its document formats such as DOCHTML, DOCMHTML, but later on these HTML based versions were discontinued. Resultantly, DOTHMLT is also no more supported.