When enlarged most favicons are rather ugly and pixellated, making them very unsightly and unusable in your dock. Fortunately, this problem can easily be fixed in just a few minutes.

Just open your favorite image editor, and make larger favicon. 100px by 100px should work just fine. Personally, I really like Opacity, because it is very easy to make gorgeous application icons in under 10 minutes. 

If you would prefer not to replace your current favicon you could make a different icon, place it somewhere on your server, and encourage users to download and use it, instead of your favicon in Fluid.

Little things like this will probably make your readers very happy, as it will spruce up their dock.