I had the same issue some days ago when installing skype. You need to enable the installation of i386 packages and then install libqtwebtkit4:i386
dpkg --add-architecture i386
apt-get install libqtwebkit4:i386
If the last command returns an error about overwriting some files, it's a bug in the i386 version of libqtwebkit4 that's easily solved by forcing its installation. Workaround
EDIT: Be aware that if you use aptitude, it doesn't throw any error, but doesn't install the package all the same, so you might have to follow the linked workaround.