WebView (QtWebKit 3.0): unresponsive UI and weird button style

[acepublic]

Hello everybody,
I tried integrating a HTML page into my Qt Quick/QML application (Qt 5.3.0) using a WebView (import QtWebKit 3.0). The HTML page is shown but with a weird button style (round buttons) and a very unresponsive UI (noticable delay when clicking button or input box in HTML page).
The same page is shown perfectly normal in a QWebView or using the old WebView (Qt 4, import QtWebKit 1.0).
I observed this behavior both on Windows 64-bit (ANGLE) and Linux 64-bit, both Qt 5.2 and 5.3.

The page is included as

@import QtQuick 2.0
import QtQuick.Window 2.0
import QtWebKit 3.0
//import QtWebKit.experimental 1.0

Window {
WebView {
id: webView
anchors.fill: parent
url: 'http://localhost/mypage.html'
}
}

@

The HTML page uses AngularJS. If necessary, I can make the source available.
Any idea what I am doing wrong?

Thanks,
Andreas