I would be inclined to agree with IanDB, it sounds as if you have quite a bit or moss. If it is really bad you may want to hire a motorised scarifier after the moss killer has done its job. The moss will slowly reappear overtime unless you keep on top of it with regular raking.
Your lawn may look incredibly bare once you have removed most of the moss, so you may want to put some seed down quickly before the weeds get chance to flourish.