-----Original Message-----
>From: Yahya Abdal-Aziz <[log in to unmask]>
>Hi Paul, and others,
>On Tue, 6 Jun 2006 Paul Bennett wrote: 
>> That'll make a passable (but non-optimal) Windows .ICO file.
>To make an optimal one, you need to define 
>the criterion or objective function to optimise.
>And what was your criterion of optimality,

The best Windows .ico files (relative to the needs of most content creators) contain multiple versions for display, usually several sizes and color depths. Letting Windows do the conversion for display produces results of variable quality, by which I mean the algorithm can't know which features of your particular icon are most important to you, as a content-creator.

>> The kind of icon I think the OP was asking about (that appears in 
>> the Address Bar, and in your Bookmarks) is called a favicon, 
>> about which see which 
>> contains a very instructive guide.
>And which is just an icon, after all, for which
>the choice of a particular name and location
>gains certain default behaviours, nicely
>explained in several references

Yes, but merely knowing how to make a compatible file is not the same as knowing how to use it to best suit your purposes.

>I don't believe the original question asked for
>"optimality"; rather, it was just "how do you 
>make ...?". 

And your answer was how to make an .ico file, not how to make a favicon, which (as you rightly note) is more than just a grid of pixels.