An intermediate in the combustion of carbon and hydrocarbons, carbon monoxide, is of special importance because it is a poisonous gas, but also economically useful for the production of syngas. Solid and heavy liquid fuels also undergo a great number of pyrolysis reactions that give more easily oxidized, gaseous fuels.
GM is short for General Motors. in text means Good Morning or means Good Move. Also means Genetically Modified.
XD, :P, :) etc stand for denoting emotions while chatting. In services like Yahoo Messenger, you already have a set of emoticons available for insertion in the text. But you can use the code names too. Look at them sideways and you will see they are what is called smileys or emoticons, as the last person who answered said, they represent different emotions. XD is a laughing smile. :P is face with tongue out.