Change favicon of bookmarklets

I have a folder of bookmarklets. They all have the same favicon, i.e. the default (globe) icon. It would be useful to change at least two of them to distinctive icons.

I copied code posted recently on another forum. It is only partly effective in that the default icon disappears but, instead of the icon I have named, there is a faint orange blur. The icon I have named is the Facebook icon, a white f letter on a blue background. I began with an .ico file but changed it to a .jpg file, hoping that would help; it didn't. I also tried changing the size from 1616 to 2424 and 50*50, to no avail.

The code is below.

#personal-bookmarks .bookmark-item[scheme="javascript"][label="zap fb"] .toolbarbutton-icon,
#personal-bookmarks .bookmark-item[scheme="javascript"][label="zap fb"] .menu-iconic-icon {
width: 0 !important;
padding-right: 16px !important;
background-image: url ("fb16.jpg") !important; }