Web-to-Lead Form Mapping of Title

Web-to-Lead Form Mapping of Title

The code for the web-to-lead form maps the Designation field to the Title field in the Lead and not the Salutation field.  How can this mapping be corrected?  Or how can a value for the Salutation be set?

I am generally confused as to why there is a Title field and a Salutation field - what is the difference?  Salutation is a pick list and therefore contains titles (Mr,Ms etc.).  Title is a text field but it is not clear what values would go in here.