It may not be only related to the browser's video rendering!!
Please look at my examples of the Horizontal lines that I have:
http://postimage.org/image/lihagn8px/
Looks like the ones that the one posted by Mike in Tampa Bay
Now the most interesting thing.
When I sterted having these horizontal lines I suspected that it may be a GPU hardware problem.
I went to my local Apple dealer - Saturn (Berlin, German) and the Apple Customer Service guy pointed me at
this
https://discussions.apple.com/thread/4148522?start=90&tstart=0
topic and informed me that it is definitely a browser's rendering issue. And I thought that it was ever since.
Three days later after I watched a movie and played a video game I started my Logic 9 and I noticed this:
http://postimage.org/image/xml153noj/
Do you see these 2 black lines? It means that the problem is not only in video rendering of the browser's ouput.
For me it still seems like it is a hardware problem.
I've been using computers for last 20 years and I have never seen that any software could cause such video artefacts. I hope that I am wrong, becaus if it is a harware problem it will be very hard to make Apple to exchange the GPU or the entire logic board until it wil die completely. And the thing that it may happen after 2-4 years of the use of the computer, when it will be out of warranty and apple care 3years limit.
Similar thing happened to some of Apple Macbooks users with ATI Radeon X1600 mobile and the GPUs on 2006 and 2007 Macbook Pros.
Here are the links:
http://reviews.cnet.com/8301-13727_7-10330060-263.html
I am using Macbook Pro 15" Mid 2012, Intel + Nvidia GT650 GPUs.