<img src="../images/dragonfly.gif" alt="[dragonfly missing]" title="Dragonfly art by ideveloper">

alt is used if the image is not found.

title is what shows when you move cursor over the image.\

Please mark "Solved" one answer that will best help others with a similar problem -- hope this was it.

thanks but when we not provie alt and title to a image

My reply to your other post was lost when that thread was locked. (Insert sad face here.)

If your page is rendering in Quirks mode, then Firefox will display a placeholder. It does not natively do that in Standards mode, but you can force it with a user style (see, e.g., the July 19th reply in this thread: base64 - CSS transparent background image using "data:" - Stack Overflow).

Or, if you want to use a script solution (e.g., Greasemonkey userscript), you can identify the missing images with this:

var missingimgs=document.querySelectorAll("img:-moz-broken");

Or maybe there's an add-on??