See: * http://kb.mozillazine.org/Image_tooltips_do_not_work *[https://developer.mozilla.org/en/Mozilla_Web_Developer_FAQ#Why_doesn.e2.80.99t_Mozilla_display_my_alt_tooltips.3f Why doesn’t Mozilla display my alt tooltips? (MDC)] The [http://www.w3.org/TR/html401/struct/global.html#title title] attribute is meant to show as a tooltip if you hover an image or link and the [http://www.w3.org/TR/html401/struct/objects.html#alternate-text alt] attribute is meant to be displayed if the image is not available. If there is no title attribute, but there is an alt attribute then IE will show the alt attribute as a tooltip. Firefox doesn't do that, so if the title attribute is missing then you do not see a tooltip if you hover an image or link.