Help me figure out strange parameters in Multipart Request Entity

Question

I am trying to analyse file uploading in FileDude.com

When i upload a file, a post request is sent with a multipart request entity which contains 3 parts. The first one is "Filedata" which contains the file data and the others are named "x" and "y" with some values. These values differ each time I upload a file(even if it is same file). X is like 77, 100, 47 and Y is like 11, 10, 13.. I don't know how these values are being calculated. Can anyone figure this out?

Answer 1

The page is using a form with an image as "submit" button:

    <form action="http://srv4.nl1.filedude.com/upload" method="post" enctype="multipart/form-data">
        <input name="Filedata" type="file" size="45"><br/><br/>
        <input type="image" src="http://static.filedude.com/templates/normal/img_en/upload.png" /><br/><br/><br/><br/>
    </form>

The X and Y values are the coordinates of the location where the user clicked in the "submit" image.