Xamarin.Forms WebView Control in Windows Phone 8.1 App

Hi,

I have developed a rather simple Forms App which has a Forms WebView control on a TabPage.
In the WebView control a mobile website (with jQuery behind I think) is displayed.

The Android and iOS version runs fine in the emulators.

Then I created a Windows Phone 8.1 Silverlight application with VisualStudio 2013 SP2 and added both my Forms PCL project and the necessary Xamarin.Forms NuGet Package for Windows Phone.

The app compiled and runs BUT the display of the mobile website is rather poor !!! No CSS seems to work neither the jQuery stuff.

Is this a problem of the Forms WebView implementation on Windows Phone ?
Do I make a mistake ?

I just provide the WebView control with the URL, that's it. I can do nothing more than rely on the WebView control rendering capabilities !?

I have added two screenshots, one of the iOS app and one of the WindowsPhone app displaying the same mobile web site page.
(I think even if the text is in german everyone can see the huge difference of the display result)

Any ideas ?

Best

Marco