This is interesting, data embeded in an URL – RFC 2397
I saw this on hackzine today, very interesting, time to ponder some uses.
I discovered a URI called "data:" today which allows you to encode any amount of file data into a URL. This data could be an image, ascii text, xml data, you name it. You'll have to read the details, but you use it like this:
data:image/jpeg;base64,base_64_encoded_jpeg_goes_here
The hackzine article: http://www.hackszine.com/blog/archive/2006/11/rfc_2397_embed_image_data_insi.html
The RFC 2397