That's called a "Favicon" and it's sent by the website for every page or page refresh you make. You can remove it by deleting browser cache. But that will only last until the next time a page on that site is visited. To remove it permanently, note the name of the icon before you delete it. Then load a transparent image in the cache folder and give it the name of the one you just deleted. Then never delete cache again! Favicons are 16px x 16px in size, and typically .png files. If the one you delete has a different file extension (e.g., .gif or .ico), you should use the same thing when you replace it. You should be able to find transparent ones online that you can use.