When calling PROCESS HTML TAGS there may be situations where the 4D HTML tags are evaluated. For instance, in your HTML file if you have:

<!--4DVAR variablename -->

And the tag is not evaluated after calling PROCESS HTML TAGS try this:

1. Go to Design mode
2. Go to Preferences
3. Go to Application -> Compatibility
4. Under Web Compatibility enable "Use 4DVAR Comments instead of Brackets".

By default this option is selected in a new database created in 4D 2004. However if you have an upgraded database it may not be selected.