Convert javascript popup content to URL from div content

[Benjamin Alexander]

Hello everyone,
I am trying to use a popup script that I found online and am having trouble understanding how to convert what is displayed from content that is listed on the HTML page and called via a getElementByID() to a URL that then gets inserted into the popup. I like this script because it uses a balnket function to create a dampening of the page behind the popup while the popup is active. So what I need is this same script to be converted to displaying a URL. Been looking around but all of them seem to (again) be stand alone scripts and since I am just learning Javascript I can't (yet) figure out how to modify this one without screwing it up in some way. I know I will know how to after this and this same post will most likely be useful to others once it is answered. So here goes:
CSS_POP.js

function toggle(div_id) {
    var el = document.getElementById(div_id);
    if ( el.style.display == 'none' ) { el.style.display = 'block';}
    else {el.style.display = 'none';}
}
function blanket_size(popUpDivVar) {
    if (typeof window.innerWidth != 'undefined') {
        viewportheight = window.innerHeight;
    } else {
        viewportheight = document.documentElement.clientHeight;
    }
    if ((viewportheight > document.body.parentNode.scrollHeight) && (viewportheight > document.body.parentNode.clientHeight)) {
        blanket_height = viewportheight;
    } else {
        if (document.body.parentNode.clientHeight > document.body.parentNode.scrollHeight) {
            blanket_height = document.body.parentNode.clientHeight;
        } else {
            blanket_height = document.body.parentNode.scrollHeight;
        }
    }
    var blanket = document.getElementById('blanket');
    blanket.style.height = blanket_height + 'px';
    var popUpDiv = document.getElementById(popUpDivVar);
    popUpDiv_height=blanket_height/2-200;//200 is half popup's height
    popUpDiv.style.top = popUpDiv_height + 'px';
}
function window_pos(popUpDivVar) {
    if (typeof window.innerWidth != 'undefined') {
        viewportwidth = window.innerHeight;
    } else {
        viewportwidth = document.documentElement.clientHeight;
    }
    if ((viewportwidth > document.body.parentNode.scrollWidth) && (viewportwidth > document.body.parentNode.clientWidth)) {
        window_width = viewportwidth;
    } else {
        if (document.body.parentNode.clientWidth > document.body.parentNode.scrollWidth) {
            window_width = document.body.parentNode.clientWidth;
        } else {
            window_width = document.body.parentNode.scrollWidth;
        }
    }
    var popUpDiv = document.getElementById(popUpDivVar);
    window_width=window_width/2-200;//200 is half popup's width
    popUpDiv.style.left = window_width + 'px';
}
function popup(windowname) {
    blanket_size(windowname);
    window_pos(windowname);
    toggle('blanket');
    toggle(windowname);     
}

HTML CODE THAT CALLS THE FUNCTION

                    <div id="blanket" style="display:none;"></div>
                    <div id="popUpDiv" style="display:none;">
                    </div>

HTML THAT CLOSES THE FUNCTION

<a name="pop" href="#magnacharta" onclick="popup('popUpDiv')" >Click to Close this Window and Return to the Main Website</a>

So what I need is for this to open up the contents of a URL on another server, like this one: http://doh.dc.gov/service/birth-certificates. So can anyone help me with a fix for this one?