Burn marks on iMac Screen I'm wondering has anyone seen anything like this before? Was using my 2009 Unibody iMac this morning and noticed black, burn-like, marks appear on the screen gradually. 

The machine wasn't under heavy usage or anything, however the screen felt extremely hot to touch.

The previous week there was condensation looking areas behind the glass.

Any input appreciated, thanks.
This happens all the time. 

Condensation and fog like effects are almost always benign and transient. Shut down form15 minutes minimum and restart. 

The image persistence is somthing all LCD will eventually succumb to and some can show that even when brand new. Either power off entirely for hours or days or have an all white screen saver engage and prevent partial content from staying on screen static. 

https://en.wikipedia.org/wiki/Image_persistence