Websites are represented by the BibTeX-Type @misc. This Type is used, if no other type can be applied.

Title, Howpublished (URL), Month Year, note (optional).

iavas, http://www.iavas.de, June 2004, Interactive AudioVisual Application Systems, home of the i3d player.

@misc{iav04,
   title="iavas",
   howpublished="http://www.iavas.de",
   month=jun,
   year=2004,
   note="Interactive AudioVisual Application Systems, home of the id3 Player"
}

BibTex-Attributes:
Must contain: none
Can contain: author, title, howpublished, month, year, note