Xclear

Icons in the URL, search and find fields to clear their contents. This is mostly useful for X-windows users who don't want their clipboards to be erased when marking the text in the field to delete it. Unlike some similar add-ons, this one is really lightweight and doesn't need any toolbar buttons. The functionality is like the ones found in Konqueror.

The look and visibility of the icons can be customized through the userChrome.css file:

To disable the icon in the URL field, add:
#urlbar * .xclear {
display: none !important;
}

To disable the icon in the search bar, add:
.searchbar-textbox * .xclear {
display: none !important;
}

To use the old, more Gnome-like X icon, add:
.xclear {
list-style-image: url("chrome://xclear/skin/clear.png") !important;
}