You can send automated emails to your new contacts using the Email Notification option provided while creating the web forms. See Also Creating Web Forms.
You can also create an Auto Response Rule that allows you to send automated emails when a specific rule criteria is satisfied. When a lead is generated through web forms, you may want to send appropriate emails to the leads with different types of requests. In such cases, you can create an auto response rule with specific rule criteria. When a condition is satisfied, the corresponding email is sent. You can create many auto response rules but only one auto response rule can be active at a time. See Also Auto Response Rule for Web Forms.