Remove the default browser header and footer when printing HTML
Google Docs is now skirting around this issue by generating a PDF version of your document.
If you are using Chrome, it will automatically open the PDF in a new tab and pop up the print dialog. Other browsers will prompt you to download the resultant file (which is not necessarily obvious behavior).
While I don't find this to be an elegant solution, one should be able to recreate this fairly easily using most existing web technologies.
These a usually browser specific print settings.
In IE & FireFox for example you can go into page setup and change the header and footer details for printing.
I don't think this can be controlled by the web page itself.