IE8 Transparency / Opacity explination

IE8BackgroundOpacitySolution.css

/* 
   This is based on the assumption that the .pop-background element is inserted into the DOM at the bottom of the page after initial page load when the modal is initiated on click. 
*/
.pop-background {
    /* Works when inserted into the DOM after page load. Data-uri's work as well as hosted images. */
        background: url("data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAAEAAAABCAYAAAAfFcSJAAAAGXRFWHRTb2Z0d2FyZQBBZG9iZSBJbWFnZVJlYWR5ccllPAAAAA9JREFUeNpiYGBgiAEIMAAAYQBdPMcrbwAAAABJRU5ErkJggg==") 0 0 repeat;

    /*
        Does not work when inserted after the DOM is initially loaded for the first time. The element will have no opacity filter applied.
        background: black;
        filter: progid:DXImageTransform.Microsoft.Alpha(opacity=30);
    */

    /*
        This opacity will display correct however all of the hover states behind the modal window such as links
        navigation hover states will still be activated when the user mouses over them. The modal background .pop-background
        does not prevent interaction with page elements.
        -ms-filter: "progid:DXImageTransform.Microsoft.gradient(startColorstr=#99000000, endColorstr=#99000000)";
    */
    
    width: 100%;
    z-index: 999;
}