The change to 8.1 + Lumia Cyan official will bring this on...
Microsoft then tweaked the User Agent string and other factors in Mobile IE. Download
SysApp Pusher and use that to make sure all your components are as up to date as possible.
Open SysApp > tap the "check" button on the left in the lower tool bar.
I have been on Official 8.1 + Cyan with a 1520.3 since August when I unboxed my phone and updated it with the Lumia Software Recovery Tool. The IE experience has gotten much better as Microsoft pushed updates to mobile IE.
@ dKp1977, the OP probably just unboxed a 1520 which shipped with Black and the last figure I saw from AdDuplex from December, 2014 showed only 53% (or 57% ???) of Windows Phones accessing the Store had updated to Cyan...