website conversions

we have experienced a serious drop in conversion rates from July 24 on and can't find out what has happened. Traffic is down a bit but CR dropped more than usual. When some one filled out form to get free quotes they can do it from home page which has seen drops and from our main affiliate site (iframe) which has seen drops. detective work needed. I would like your recommendations on improving conversion rates with our online form (free service), Also look at why our CR went down 2% points since July 24th, and help set-up/change our Google Analytics funnels to show proper exits and CR. Can you help us?