Q: Greyish Smudge marks behind the glass screen.

and what action have you taken to resolve this?

It does appear to be similar to other snapshots of screens that I've seen on here. Mine looks a little different, but yes, I'd say you have the same problem developing.

There are several actions being taken online if you google the same subject. I'll probably get deleted here, but subscribe to this thread and get email notifications. That way you will see links that are posted and then taken down by Apple. My twitter is @Omek.

and this is not something with dirt under the glass as I was hoping for a second? ((( I am not technically strong, so do appologise for stupid questions..... is this something with the screen? What people do with this damages?

I may have been lucky, but Apple replaced my LCD panel a couple of months ago on an iMac that was just over a year out of its warranty. May depend on who you can get hold of at Apple when you contact them. I'm in the UK by the way.

it's certainly not universal response...can't get mine even acknowledged here in New Zealand/Australia...startd when living in India and they said environmntal ...sorryYashik...not fixable...even when screen replaced frequently seems to comes back...you'll find all sorts of experiences from Apple support recorded here...Australian/NZ say won't replace after expired warranty..go immediately to warranty support before expires...you may be lucky!

There's not a conesus to whether this is dirt or not. The screen doesn't seem to be properly sealed. However, I think it's more a of a problem of the LCD being too close to the internal hardware. As the machine gets used for more intense tasks, things heat up and cause some of the cells in the LCD to burst, hence creating the smudge-like effect. That sounds like the most plausible  explanation to me, but it could also be dirt and dust getting sucked into the back of the monitor, because it's not properly sealed. It's really hard to say.

An explanation from Apple would be nice, but we still haven't gotten one yet.

You can go to your nearest Apple Store or Apple reseller and see what they can do, but I've seen most screen replacments have been a temporary fix. The hardware design seems to be the flaw, so it's going to require a complete overhaul of the entire machine.

I don't know it its LCD bubbles bursting - in my case it could flare up, and calm down, usually depending on heat. Plus it would shift a bit - usually it was a jagged line, but sometimes perfectly straight.

having experienced this - and observed the process - (I'm not expert - but have used macs since the mid 90;s) - It seems to be a 'heat' issue.  My brand new mid 2011 imac was the 'hottest' computer I'd ever owned. I would wake up in the morning, and go into my living room and wonder why it was so warm.  (bearing in mind I live in London, UK).

First of all the hard drive failed after about 6 months, and I just thought - 'these things happen'.  Though I was still concerned about the heat it was pumping out - but still just thought it was how 'new' Imacs were. 

Then occasionally the imac would randomly put it the 'screen' to sleep.  (not the whole system, as processes were still happening in the background and I could hear the drives running.)  This became more frequent  - and was the initial reason I contacted apple again (11 days out of warranty) to get it fixed.

I hadn't even noticed the discolouration of the screen until I was waiting in the apple store in Brent Cross (under it's bright fluorescent light) waiting to speak to them about why I'd contacted them.  The 'smudging' was mainly contained to the upper left quarter of my 27" screen - but also seemed to have 'spread' down most of the left hand side of the screen, too.  Apple called this 'contamination'  (and made me feel as though it was 'my fault' and they would fix it 'as a favour'.)  I wasn't impressed with the service (for the first time in 20 years).

However - since they have replaced the Power Supply, LDC Panel with BLC and Glass panel - all seems to be working fine.  The imac is nowhere near as hot as it used to be - even when I'm running processor intensive apps.

I didn't break it, Apple.  It was broke already.

To Yashik.san.

It isn't 'dirt', it is rather more serious. I documented my machine's problem on a previous page.

The heat affects the polariser layer in the LCD screen - as a result areas of the screen take on a smudged/stained appearance.

There isn't any dirt (in my case anyway).

After a load of silly excuses from Apple I took my 2011 iMac apart to verify this.

You killed all my naive hopes.... I have my diploma defention in 2 weeks and untill than won't be able to ask Apple for repair, but hope to resolve this problem afterwards

oh -- i forgot to mention that the only way i could 'bring the screen back to life' (when it randomly went blank) was to actually put the machine to sleep by pressing the main power button once.  Wait for the imac to actually 'sleep' and then 'wake it' as usual, but pressing the space bar or something, All the things I was working on etc - were exactly how they were.  not sure if that helps anyone.  just saying. 

To Packjoker:

There's a very thin ribbon data cable that links the screen to the main board, this can easily come loose. It's the ZIF type with the latch. By contrast the cable which powers the backlight seems reasonably secure.

is that what happened to mine? perhaps it was getting hot or somthing... I don't really have any technical knowledge of these things. and i don't know what a ZIF type is (nor do I need to!  ) all i know is it is no longer overheating - that was worrying me the most.  but thanks.