HTML is an acronym for the HyperText Markup Language. It is by far the most common means of expressing information on the World Wide Web. For more information on HTML, visit the Computers: Data Formats: Markup Languages: HTML category.
Sites to do with free HTML editors are best submitted to Computers: Software: Freeware: HTML Editors.
Sites with information on software which takes data in one format or another and produces HTML web pages belong in Computers: Software: Internet: Authoring: Converters
If your site describes an editor that produces web pages for users who do not know HTML, it will likely belong in Computers: Software: Internet: Authoring: HTML: WYSIWYG Editors ("What You See Is What You Get").
This category is for tools which only check a page or site. Editing software which include this feature should go one level up.