B757 first officer describes the events leading up to the shattering of his forward windshield and the decision to divert.

Narrative

About 2 hours and 15 minutes into the flight I looked up and noticed a 5 cm bubble in the right forward windshield in the lower right quadrant. It had what looked to be a string about 50 cm long running from the bubble to the lower left edge of the windshield. At the lower left edge of the windshield there were two burnt marks. In the string; it looked like there may have been some liquid. I showed the Captain and suggested we shutoff the window heat. He agreed; and I shutoff the window heat to that window. After about a minute I thought; warm window; some burning or melting; and very cold outside air. I said 'I wonder if it will shatter.' One minute latter - bang - it shattered. The captain took out the QRH. After reading the procedure; he decided if his windshield shatters it would be difficult to land the airplane and it would be more prudent to land the airplane. We declared an emergency and landed without incident. This was my first shattered windshield at the airline however; I have had three or four on the C-141.