Hi I'd like to know requirements for enabling users to deposit by paypal on my site. i have not got any experience
You will need at least a Premier or Business Paypal account. What do you mean by 'deposit by paypal' ? Paypal does not permit you to run a financial institution by offering banking services such as deposits. It only allows you to receive payment for sales or for sending money to friends.
I assume you mean that you are selling a product or a service. If that is so, all you need is a Premier or Business Paypal account. Have that verified legally and that should do the trick. You could then make use of the Buy Now or Donation button option in paypal. However with all that said and done, you will need to be from a country which supports receiving of funds in the first place. Check this list https://www.paypal.com/cgi-bin/webscr?cmd=_display-approved-signup-countries-outside Make sure what you are offering is not prohibited by http://www.paypal.com/cgi-bin/webscr?cmd=p/gen/ua/use/index_frame-outside because some members have their accounted limited because they ignored these.