Credit spreads

Hi Everybody !!!!!!
I am doing little bit of option trading. Can anybody suggest any software or website or subscription service that will provide me CREDIT SPREAD opportunities at NSE on regular basis.

Hi! Believe me this is something that I am really not at all conversant with. But I am interested. Can you please tell me what this thing about credit spreads is all about? Don't bother if it is too complicated and you feel that as a layman I may not be quite able to pick it up. By the way, I'm into straddle positions in the nifty (only) and .... well, I suppose you must be knowing much better than me about this too. Suggest some practical tips if you might be having some. Thanks. (Maybe you could mark your reply to my id so it would be easier for me to pick it up, thanks!)

Hi everybodies:
I have few questions about the credit spread.
Once execute the credit spread, the margin will fixed
between the sell side and the buy side? or they will fluctuate
by the up and down of the underlying?
Any one could help, thank.