In versions of 4D prior 4D v6.7.1, the web server tolerated bending the rules for writing pathnames if a default HTML root folder was defined in the database properties: the HTML root folder could be included in the pathname of other pages of the site.

For example:
Default HTML root: WebFolder
Default home page: WebFolder/index.html

With 4D v6.7.1, these settings will generate an error because 4D will look for the WebFolder/WebFolder/index.html page.

In this case, the following settings are correct:
Default HTML root: WebFolder
Default home page: index.html

Note:
This situation also applies to links. In your HTML code, linking to a page with "<a href = "WebFolder/page2.html" >" will result in an error. Therefore, the correct way to link to a page when using 4Dv 6.7.1 is "".