Hi Christian,
you are right and so is Norman:
I set the PopupMenu (in HTMLViewer) to native, add the code to change it in App.Open, run and the application does not works as intended.
I commented the code, set the PopupMenu to WebKit and the application works fine.
Case close (if someone can update the documentation )
http://documentation.xojo.com/index.php/HTMLViewer.Renderer
It has always been there.
The last line.
“Setting this property at runtime has no effect.”
Hi Tim: I read that, but a problem still exist: everyone is able to place a code to do that. (and some can forgot about it when the time to debug the application comes.
The page have been changed yesterday (re-read the page at its bottom and read here : thank you Norman.
The added sentence is:
Setting this property at runtime has no effect.(to be 100% understandable by non english native folks, I would use: (Setting this property by code at runtime has no effect. )
Just for fun:
This property is only available on the Windows platform.is false: I can see it when I open the project on OS X. Of course, this is how I can understand this statement with my limited second language knowledge.
There’s no other way to set it at runtime so saying "by code at runtime is superfluous 
Now, the documentation is OK (for me).
Renderer is displayed as ReadOnly.
Thank you all.