writing to txt, clipboard?

I am attempting to pull x, y, coordinates from a webpage and write them to a txt file. So far all I have been able to do is write to a popup window.

In a nutshell I want to interatively save a list of x,y coordinates to a file.

Modify a cookie script? Copy to clipboard then paste to notepad?

any thoughts would be appreciated.
thanks

the best thing is, I guess, to use a server-side application.