Internet Explorer v8 and Opacity Issues

A great WordPress plugin jQuery-lightbox (JQLB), used to provide animated slideshow-like viewing of images in a post seemed to be having some undesired behavior on sites viewed with Internet Explorer (IE) v8 – the plugin’s jQuery based javascript was unable to successfully set the opacity of an “overlay” <div> it created in process of showing images. All worked fine in Firefox (FF) and IE v9 but would fail (though not all the time) in IE v8 (unable to test IE v7 but it may also have similar issue). Some more testing seemed to confirm that all versions of the JQLB plugin were affect as were all versions of jQuery, but the issue only affected Windows 7/IE v8. 

Some background: When invoked JQLB’s jQuery javascript will create a <div class=’overlay’>, set its height and width equal to the page size, set the background color to black, and absolutely position it to top:0, left:0 so it covers the entire page. It also sets the <div> opacity to 80% to give a transparent affect so the underlying page is still partly visible.  On some pages and using IE v8 the affect failed and there would be no opacity with only a completely black background.

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