If you want to translate tagged documents like HTML or XML files with MetaTexis, you need to use the MetaTexis command to open file. You should NOT use the normal the Word command File | Open. For, when you do this, the HTML document will be transformed into a Word document (or, if FrontPage is installed on your computer, the document will be opened in FrontPage). Of course, you can also translate a converted document. However, if the final version is supposed to have the same HTML code as the original document, this is not recommended, because Word produces a very complicated HTML code (which is optimized to make HTML pages look like Word documents).
For this reason, MetaTexis includes a separate open file command which opens tagged documents as text documents. To open a tagged document as a text document, execute the menu command: MetaTexis | File | Open (or click the related symbol in the toolbar/ribbon) and select the document to be translated. You will then be asked by MetaTexis if you want to translate the document with MetaTexis and, if you confirm, the Start Assistant will be launched.
Note: To translate tagged documents, you should at least know the meaning of the most important tags. In any case, you should not delete any tag without knowing exactly what consequences this will have.