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jModal
from Tolansky
jModal is a small jQuery plugin for customisable modal popups, released freely under the Apache license.

When run, a modal element is added to the page that pulls in content as instructed; its appearance is generated based on a set of predefined options and can be passed any user-defined custom CSS classes for additional theming (see examples below).
YUM YUM? HAPPY THOUGHTS NO ACCOUNTING FOR TASTE
Install by referencing the js file:
<script src='scripts/jquery.jmodal.js'></script>
Then call the function and pass in the text you want to show:
$().modal({content:'Pass text in directly'});   
OR use another element to store the HTML you want included:
$('#hiddenDivYum').modal();   // use the contents from the hidden div

// Values below represent default values (as of initial release)

$('#hiddenDivYum').modal(
{
    ///////////////////
    // Core contents
    target: this,               // OPTIONAL - pull contents from element
    content: '',                // OPTIONAL - put contents in manually
    
    // NOTE - content overrules target if they both have values.
    
    
    ///////////////////
    // Appearance
    width:400,                  // width of the popup
    addonClasses: '',           // any additional classes to add to the popup
    borderRadius: '4px',        // border radius for the popup
    top: '15%',                 // distance from the top when it appears    
    
    ///////////////////
    //Behaviour
    fadeTime: 400,              // fade in/out time
    addCloseButton: true,       // Add a close button or not
    closeOnOverlayClick: true,  // close modal on click of the overlay
    showOverlay: true,          // show the overlay (required for click away)
    
});