404 Error as /directory/&

What is it?

[silverbytes]

I find some 404 errors like:

/mydir/&

or

/directory/&

There is nothing in my code pointing to any /&
What are these? (I suspect of mailto encoded links) but I'm not sure.

[g1smd]

Run LinkSleuth over the site to be sure, then get creative with search queries to try to find the other site.

What's the referrer for those requests in your log files?