well the first problem is that the script invisible elements icon is not enabled.
see neilo's screen shots from this post:
showpost.php?p=87639&postcount=7
the second issue is the way the site is defined.
All of the webassist extensions will create any supporting files at the root of the site, and that is where they will expect to find them. In your case, though, there is a subfolder called webs, the index page is in this subfolder, it is linked to the CssMenuWriter folder at the same level:
@import url("CSSMenuWriter/cssmw/menu.css");
But the software is going to look for the CSSMenuWriter folder at the root, change the site definition to point to d:\websites\Web\Web as the site root.