How to send mail with a Subject using a Mailto URL?

I need to make a Mailto link to my website which is suppose to contain either the product name or the product page URL in the subject section. How can I do it?
Exp: When you get an email through eBay about a product you are selling or buying, you automatically know what product that email is about by seeing the product name in the subject section.
How can i do this?

How to send mail with a Subject using a Mailto URL?