All of the images on this page are 48 X 48 and you can download any of them as png's by right clicking on the image and select 'save picture as' or 'save image as', etc.
Now to save it as an (.ico) icon just left click on the image (notice a small border around the image), and select 'save', etc. These icons2 are made to comply with Vista and Win7. They should work in XP also, but in the new OS's the largest size icon displayed is 256 X 256.
It has to be done this way because I cannot place an icon image in a web page and have it displayed, so I had to use png's and you can still get them that way by following the directions.
firefox 02 01.ico
firefox 02 00.ico
No Cigarretes Blue.ico