This is a guide on how to create favorite icon (as required beside the url of a website) in Ubuntu using GIMP image Editor. GIMP Image Editor is installed by default in Ubuntu desktop and Slackware too. We don't need anything else. No converter what so ever. So here we go.

Open GIMP Image Editor from Applications --> Graphics menu.

Click File menu and choose New. In the new pane, type size 16 pixels for both Width and Height. Click OK to continue.

This tutorial shows how to remove background in a jpg image using GIMP-GNU Image Manipulation Program. GIMP can be found in any Linux distribution including Ubuntu desktop and Slackware Linux. To open GIMP in Ubuntu desktop, click Applications - Graphics - GIMP Image Editor. Here is an example of how GIMP looks like: