FIREFOX DIDN'T POST COMPLETE CODE HERE'S CODE AGAIN - WITHOUT BRACKETS

style .OnClick {height: 100%;} /style

img onclick='className="OnClick"' src="FullPathToPicture" title="CLICK TO ENLARGE PIX"

Why doesn't that code work in Firefox?

Maybe use this.className?

<style>
<!-- ONCLICK - PIX SIZE -->
.OnClick {height: 100%;width=100%}
</style>

<img onclick='this.className="OnClick"' src="FullPathToPicture" title="CLICK TO ENLARGE PIX">

Again, that works in IE - but not in Firefox

Also using this: ".OnClick {height: 100%;width=100%}" - does not work well in any browser

That's because most pictures have different height widths - so that using .OnClick {height: 100%;width=100%} would distort the pictures - pictures would elongate upwards or sidewards depending on whether original picture's width or height is larger

Using just width percent - or just height percent - automatically compensates for whichever of two is not used

Also, in most instances "width: AnyPercent%" is preferable to "height: AnyPercent%" because when browser window is downsized the width percent would keep picture width in window and only the lower height portion of pix would need scrolling - and also because in some instances using height percentage spec (rather than specific px setting) causes entire picture to disappear

QUESTION REMAINS: Why doesn't "onclick" work in Firefox?

AND - these also don't work in Firefox "onmouseover onmouseout"

sorry, width=100% should of course be width:100% for a CSS rule.

You can use max-width and min-width instead to reduce the image dimensions.
Then you can set them both to none to remove this restriction and show the image with their natural dimensions. .OnClick { min-height: none; max-width:none; }

Did you try to use "this": onclick='this.className="OnClick"'?

You can try to add the !important; flag to see if that helps.