solved-what is a graphic card average temperature? Edit: an overclock expert needed:)

87 is quite high, but probably not unheard of when it comes to AMD cards. If it starts to bump 95, you should be concerned.
My suggestions (in order of cost) would be to either clean the dust out using a brush, point another fan at it, replace the heatsink/fan on the card, or just get a new nvidia 9 series card.

If it's a reference cooler http://www.pcper.com/files/imagecache/article_max_width/news/2011-12-14/sapphire_radeon_bikini.jpg then that's normal at stock fan speeds. But you can set it to run higher under load and shorten the fan's lifespan, but better the fan than the gpu. Mine starting making a clinking noise after a while if the fan ever went over 30% when I did that, so I just got a new card. It was a more cost effective upgrade than spending $20-$40 to replace the fan since the card was getting older anyway.

I have an Asus GTX 550 Ti. It is fair to mention that it has modified cooling system by Asus (DirectCu 2). Idle temperature is around 40 and when games make it sweat, it's around 65-70 and NEVER goes above.

Normally below the melting point of Si and Fe

I'm using a GTX 760 right now and the idle temperature is usually 40C and the max temperature I have seen is 84C when playing a game.

plz answer my edited question too if anybody knows about overclock

Temperature of the card is dependent on the chip and the cooler. You can't compare it to anybody running a different gpu family or has a different cooler. Variations in case performance will affect it as well. That said, google should give you the answer easily.

As for the CPU, just download some monitoring program like CoreTemp or Speedfan.

I have an old Nvidia gtx285 which is around the same age as yours. Normal operating temperature is suppose to be 81°C but dust and age will cause it to gett hotter now. I have had it reach 101°C though I dont recommend that :)

87°C is ok, but really you want to make sure the fan blades are clean, that should drop it a few degrees. Some new heatsink paste would also be a good idea.

As for overclocking, I prefer not to since it does shorten the life of the CPU and makes it more likely to overheat.

I'm using an MSI GTX 670 with aftermarket cooling (removed the stock fan and installed an Accelero Twin Turbo II) and it never goes above 40 °C even on heavy load and on the plus side it runs completely silent. If you are concerned about temperatures, either clean the inside of your case and your gpu of any dust that may have accumulated (This is what I do every few months) or replace your stock fans with something better.

My King Arthur edition 5450 has a heatsink, overclocked it to the max. It runs at around 110 C. It overheats quite often and the heatsink is melted, but it works.

my radeon hd 7870 ghz rdition(oc by 20 % (1200 mhz)) reach 33-35 c under a 100 % load for a minut with furmark (but i have it water cooled)

my radeon hd 5570 was about 50-60 c but burn a mounrh ago D:

and my radeon hd 3670 is 82 c when i look a video in hd on youtube and it dosent want to die D: