The .ico file format was defined my MS and is thereby vcrappy, but iirc it works as follows:
It has a small header identifying it as an icon file.
It may contain 3 images, 16x16 px 32x32px and 64x64px. (why not make this "any size" or even better a vector)
the internal images are iirc bitmaps (windows style, drawn bottom, top, LSB first)
Color depth must be 8bit
I might remember wrong but i think this is about it.
if only one icon is in the file, you may ignore the header, and use a simple bmp file like you do, but its not very good to do it that way.
Edit:
You can also easily tell that the favico.ico standard is an MS invention because of its hoddible limitations:
The file _must_ be in the root dir of the webserver (thereby making it impossible to make different icons for different parts of the site)
it _must_ be called favicon.ico
if _must_ be a windows bitmap icon
idiots.
Efforts are being made to make a better standard out of this, and i think the following is now allowed and recognized by most browsers:
<link rel="Shortcut icon" href="/design/gardsplassen/images/favicon.ico" type="image/x-icon" />
the spice extend life!
the spice expand conciousness!
the spice is vital to space travel!
sooooo.. tell me what you want, waht you really-really want
I will proceed directly to the intravenous injection of hard drugs, please.
so i did one (92 bytes)... if the site admin wants to use it, simply open it, save it as a .bmp and change the extension to .ico before placing it at the website root folder :
