Robots txt and Wordpress - 404 errors

Wonder if anyone can help me.

For some reason (through my outsourcers), they have managed to direct people to a page on my site which is structured like this - .com/</a> <div> &%

And there are several pages pointing to this page and in my Google webmaster tools, I get a 404 error for the page.

I've asked Google to remove the URL (through webmasters), and I've been trying to get Wordpress to match the URL, so have a page with the address of:- .com/</a> <div> &% however Wordpress doesnt seem to like that format of URL, and doesnt allow me to create a page like that (my intention was to create a page like that and then to set preferences to no-index).

I understand I could perhaps do something with the robots txt to rectify this issue? I understand you upload it to the root directory and you dis-allow say a sub directory, however how can I mark the above page - .com/</a> <div> &% to show as non-indexed in the robots text etc?

Also even if shown as non indexed by the robots text, surely Google will still report a 404 error as there are several pages pointing to this non existent page.