My HTML/XHTML book (the Koala) says the name attribute is optional, but does not indicate how to handle this case. From a practical standpoint, without a name, it's unclear how anyone would get at the coordinates in a CGI program.

I'd suggest just submitting the form normally. Anyone who uses an image as a submit button (such as 'search' in the header up above) doesn't care where the mouse was when the user clicked. Either name your input elements, or ignore them.

If I remember, I'll dig through an RFC later.