You should use QT += webkit
, but ...
You also need to make sure you have the webkit libraries installed. Go to the following website to grab the latest QtWebKit library version: http://qt-project.org/downloads
Alternatively, you can also go to this page to get older versions if you really need 5.0.X:
http://download.qt-project.org/official_releases/qt/
Slightly off-topic, so pardon me: but you should not include the what QtWebKit module. That may cause some not insignificant overhead.