I know you can embed images in html today with:
But back in the day, when N
I don't know any other way specific to Netscape (RIP) and a quick search showed me that "IMG SRC=data:" has been supported by Netscape already in 2003.
I found out some IE specific tags that look like yours, but never used them (not sure it will help):
Some more info on embeded images in sources here (can help readers unfamiliar with this topic): http://www.websiteoptimization.com/speed/tweak/inline-images/
Here is a way to use "IMG SRC=data:" under IE6: http://web.archive.org/web/20080702001125/http://ddzoom.net/jsimages/out.htm