I have the webbrowser control and it is set to designmode like this:

theWebBrowser.AllowNavigation = False
theWebBrowser.AllowWebBrowserDrop = False
theWebBrowser.IsWebBrowserContextMenuEnabled = False
theWebBrowser.ScriptErrorsSuppressed = True
theWebBrowser.ActiveXInstance.document.designmode = "On"

I have tried something similar using IE and Firefox by running this in
the browser:

javascript:document.body.contentEditable='true';
document.designMode='on'; void 0

They both put the the page in edit mode, but the first way garbles the
page. The second works just fine, not changing anything. I have tried
a number of things, such as running the JavaScript against the
webbrowser control. But the result is the same.

I am surprised that I haven't found any mention of this anywhere