//setting the opacity of a given element to the given value
//
// elementId  -- unique id of the element (id in the DOM)
// value      -- value to set the opacity to
function setOpacity(elementId, value)
{    
    var element = document.getElementById(elementId);
    
    element.style.opacity=value;
    element.style.filter="alpha(opacity="+(value*100)+")";
}