I could never find a close or exit button.
IIRC, there is a bug related to windows font size settings that will cut off the OK/Cancel buttons at the bottom of the screen. It has been discussed over at the Invelos forum, but I don't remember what the solution was.
Alternative workaround: In the
Tools menu use
Select HTML Editor to specify an external program for editing the HTML section, e.g. notepad.exe. Use
Launch HTML Editor, edit the HTML section, save the file, and close the external program. DVDProfiler will now automatically update and save the changes to the HTML section. Finally, use ESC or Alt+F4 to close DVDProfiler's editor.