Advertise the service out of Salesforce to create the lead, and call the service with ASP.

1): How to Configure in Salesforce, advertise this service outside, please see the following link:

http://www.shellblack.com/marketing/web-to-lead/

2): How to call this service in ASP. To create the corresponding lead, see the following code:

            Try{StringBuilder Data=NewStringBuilder (); Data. Append ("Oid=[youroid]"); Data. Append ("&first_name="+ Server.URLEncode ( This. Txtfirstname.text)); Data. Append ("&last_name="+ Server.URLEncode ( This. Txtlastname.text)); Data. Append ("&email="+ Server.URLEncode ( This. Txtemail.text)); stringURL ="https://test.salesforce.com/servlet/servlet.WebToLead?encoding=UTF-8"; HttpWebRequest req=(HttpWebRequest) webrequest.create (URL); Req. Method="POST"; Req. ContentType="application/x-www-form-urlencoded"; byte[] buffer =Encoding.UTF8.GetBytes (data.                ToString ()); Req. ContentLength=buffer.                Length; using(Stream Reqst =req. GetRequestStream ()) {Reqst. Write (Buffer,0, buffer.                Length); } WebResponse Response=req.            GetResponse (); }            Catch(Exception ex) {}

For more information, see the following link: Https://success.salesforce.com/ideaView?id=08730000000Y07QAAS

3): http://www.chronoengine.com/faqs/61-cfv4/cfv4-tutorials/4112-how-can-i-send-form-data-to-salesforce.html

Advertise the service out of Salesforce to create the lead, and call the service with ASP.