This is a small and simple jQuery plugin I wrote just so I could darken an area of the browser window behind the selected elements, usually DIVs but can probably be used with other elements.
$(selector).shadeArea({    color: black,    opacity: 0.7    id: “idOfShadeDiv”});
selector is your jQuery selector.
color parameter specifies the color for the shader and can be any valid color used in CSS. Default is “black”.
opacity parameter specifies how dark the shader would be. Should be a decimal between 0.0 (not visible) and 1.0 (solid color). Default is 0.7
id parameter specifies the id for the newly created shader div. If omitted, an id of “shader_”, suffixed by the ID of the original element, or a number if the element being shaded has no ID, is generated

GitHub Repo