My Ps3 will not start

Don't listen the the above guy, he's on almost every problem trying to hock some crappy guide on eBay that you can find for free.

The YLOD as its called is common among early gen PS3s, of the CECHA and CECHB series, among others. Typically its a hardware failure, and can be as simple as the hard drive is corrupt and needs reformatting, to the most common cause, and thats the solder joints underneath the processor or graphics chip has come loose due to board flexing (Similar to the most common 360 RROD problem).

Fixing it is a matter of stripping down your PS3 using one of the FREELY available tutorials online (a good video version is HERE YouTube - PS3 YLOD Fix Part 1 of 2), using a cheap heat gun to reflow the solder by heating the 2 chips up (the heatgun I'm using is 750-1000 watts and was bought at Wal-mart for $22), letting it cool 20 minutes then putting it back together. I have rescued over ten different PS3s with this method without fail.

Also be sure to check with your local Radio Shack and but Arctic Silver thermal paste to use on the chips after reflow for heatsink dissipation. A tube costs roughly $10 with tax.