Ugly frame around webview widget

I have a simple problem and even after long research I did not find a solution so I hope that someone has a hint what to do:

When I include a webview widget in my sitemap it draws and ugly inset border around it (like the CSS inset border). In the widget settings I can not find a setting to disable the border and the documentation does not say anything about border setting. See attached screenshot.

Did anyone have the same problem and found a solution?


Did you ever find a solution for this? Is it a case of using something like:

<body style='margin:0;padding:0;'>