How Do I Pre-populate An Email Link With An Html Formatted Email

If I wanted to prepopulate an email link like: (in a really simple format, pardon for the bad example.) mailto anchor href, according to RFC 2368:

The special hname "body" indicates that the associated hvalue is the body of the message. The "body" hname should contain the content for the first text/plain body part of the message. The mailto URL is primarily intended for generation of short text messages that are actually the content of automatic processing (such as "subscribe" messages for mailing lists), not general MIME bodies.

To do as you describe, you would be better off looking into a pre-processor like PHP.