Panasonic Plasma yellow screen

Plasma with Burn in within 3 years, I bet. I've seen Week old plasma's with burn in. Plasma technology is not as good as some would make it out to be. Due to the nature of the physics of the device, it is susceptible to something called "Burn-in" When an image of any form is displayed for long periods of time on a Plasma display, they start to literally burn in or wear out that part of the screen faster than a moving picture elsewhere on the screen. ie. If you have a television that is always on one channel and that channel always displays the little logo in the bottom right of the screen (abc, cbs, speed...) that kind of thing, you will eventually actually be able to read that logo even when the plasma tv is turned off. Check your manual or the manufacturer's website for your tv, and somewhere in there, it will refer to a "half-life" of the tv. ie. if your model has a 2000 hr half life, after 2000 hours of viewing, the display can at maximum, put out 1/2 of it's total brightness output. after another 2000 hrs 1/2 again as bright. and eventually it will be so dim that it's unusable. This is a fault with Plasma technology, LCD does not have this issue. CRT used to have this issue, but advances in technology have lowered this risk. So. What you are seeing is remnants of a bright image that was more often shown on that part of the screen than anywhere else on the screen. There is nothing that can be done other than replace the unit (or the screen, but it's easier to change the whole unit). if you've had this unit for 3+ years, you did pretty well. doing the math, if you only use your tv for 2 hours a day, for the 3 years you own it, assuming a 2000 hr half life, you've broken that limit. meaning that you will have parts of your screen that are very likely half as bright as others. Nature of the beast (plasma). This is why they are not as popular as they are advertised. Try an LCD next time.

Tv have problems with it 2 backlight buffer boards,like to help the tv Plasma screen panel to stay consistantly lite with same brightness.Take ur tv back where u bough it.Trade it in for another tv this tv have deffective and dying backlight buffer boards.

The pixels in the screen are commanded by a buffer board . This board connects to the screen with the help of a wide flat connector - in your case this command circuit appears to be faulty: either the buffer circuit is failing and the entire buffer board will have to be replaced ($250 part and labor from a pro) or the connection itself appears to be slightly out of line so when heated the contact is lost and the pixels get stuck (in that case the tv will have to be completely dismantled and all the contacts to the plasma panel reseated - $200 in labor).
Ask a quote around and select the cheapest repair shop you can find.

Hey mate, very common in all makes of plasma TV's. See this how to video on to fix it, the video is for a hyundia but it is the same for your TV. http://www.youtube.com/watch?v=9NPobj0_GSo
It's pretty easy, just get a soldering iron and take your time, best of luck. Bro

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YOU MAY HAVE A DEFECTIVE Y DRIVER BOARD OR A RIBBON CABLE THAT HAS COME DISCONNECTED. THIS NOT USUALLY THE PANEL SINCE THE PANEL DOES TURN ON. TAKE IT TO AN AUTHORIZED SERVICER.

If you wish to get some details; visit the site linked here. Pull up older posts.
http://electronicshelponline.blogspot.com/
Line faults & possible causes to LCD, DLP & Plasma screen are given with illustrations. You can get an idea about the fault to an extent. Faults to all LCD & Plasma screen are similar, irrespective of its brand and screen size.

need the model # so i can help you further

This sounds like one of the driver boards at the bottom or top of the screen has an intermittent fault. The set will have to be taken in to a service centre.