README.md

Above is the code Comcast is injecting into their customers web traffic when they need to display an "important message".

Feel free to read the blog post that goes along with this code.

ComcastInject.html

<script language="JavaScript" type="text/javascript">
// Comcast Cable Communications, LLC Proprietary. Copyright 2012.
// Intended use is to display browser notifications for critical and time sensitive alerts.
var SYS_URL='/e8f6b078-0f35-11de-85c5-efc5ef23aa1f/aupm/notify.do';
// var image_url='http://servicealerts.comcast.net:8080/images/mt';
var image_url='http://xfinity.comcast.net/constantguard/BotAssistance/notice/images';
var headertext1='<strong>Comcast Courtesy Notice</strong>';
var textline1='You have reached 90% of your <b>monthly data usage allowance</b>.';
var textline2='Please sign in for more information and to remove this alert.';
var acknowledgebutton='<a href=\"#\" onClick="document.location.href=\''+SYS_URL+'?dispatch=redirect&redirectName=login&paramName=bmUid\'" title="Sign in to acknowledge" style="color: #FFFFFF;"><img alt="Sign in to acknowledge" src="'+image_url+'/mt_signin.png"/></a>';
var verifybulletin='<a href="http://customer.comcast.com/help-and-support/internet/data-usage-plans-nash/" target="_new">How do I know this message is from Comcast?</a>';

if(self.location==top.location) {
document.write('<style type="text/css">');
document.write('#comcast_content {width: 600px; height:240px; box-shadow: 10px 10px 5px #888; background: #fff; border: 1px solid #454545; position:absolute; top:50px; left:100px; zoom:1; z-index: 9999999; opacity:0.90; filter:alpha(opacity=90);}');
document.write('#comcast_content .header {height: 35px; background:url('+image_url+'/headerbg.gif) repeat-x;}');
document.write('#comcast_content .a {color: #00a3e0;}');
document.write('#comcast_content .logo {float:left;}');
document.write('#comcast_content .content-wrapper {padding-left: 18px; padding-right: 15px; padding-bottom: 12px;}');
document.write('#comcast_content .headerimage { margin-top: 15px;}');
document.write('#comcast_content .header1 {margin: 18px 0 0 0; color: #C00000; padding: 3px; font: 23px/24px bold Arial, Helvetica, sans-serif;}');
document.write('#comcast_content .textcontent {margin: 12px 0 0 0; text-align: center; color: #303030; word-spacing: 0px; font: 14px/15px Arial, Helvetica, sans-serif; line-height: 1.20;}');
document.write('#comcast_content .acknowledge {padding-top:6px; text-align: center;}');
document.write('#comcast_content .how-do-i {float:left; position:absolute; bottom:20px; left:18px; margin: 12px 0 0 0; font: 13px/14px bold Arial, Helvetica, sans-serif; text-align: bottom;}');
document.write('#comcast_content .comcast-wrapper {float:right; position:absolute; bottom:15px; right:18px; padding-top:0px; text-align: right;}');
document.write('</style>');
document.write('<div class="main-wrapper" id="comcast_content">');
document.write('<div class="header" onmousedown="javascript:dragStart(event,\'comcast_content\')">');
document.write('<img src="'+image_url+'/xfinity-logo.gif" alt="Xfinity" class="logo"/>');
document.write('</div>');
document.write('<div class="content-wrapper">');
document.write('<p class="header1">');
document.write(headertext1);
document.write('</p>');
document.write('<p class="textcontent">');
document.write(textline1);
document.write('</p>');
document.write('<p class="textcontent">');
document.write(textline2);
document.write('</p>');
document.write('<p class="how-do-i">');
document.write(verifybulletin);
document.write('</p>');
document.write('<div class="acknowledge">');
document.write(acknowledgebutton);
document.write('</div>');
document.write('<div class="comcast-wrapper">');
document.write('<img src="'+image_url+'/message-by-comcast.gif" alt="Message by Comcast"/>');
document.write('</div>');
document.write('</div>');
document.write('</div>');
}

// Function to Determine browser and version. Copyright 2001 by Mike Hall.
// See http://www.brainjar.com for terms of use.

function Browser() {  
var ua, s, i;  
this.isIE  = false; 
this.isNS  = false; 
this.version = null;  
ua = navigator.userAgent;  
s = "MSIE"; 
if ((i = ua.indexOf(s)) >= 1) { 
	this.isIE = true; this.version = parseFloat(ua.substr(i + s.length)); return; 
}  
s = "Netscape6/"; 
if ((i = ua.indexOf(s)) >= 0) { 
	this.isNS = true; this.version = parseFloat(ua.substr(i + s.length)); return; 
}  
s = "Gecko"; 
if ((i = ua.indexOf(s)) >= 0) { 
	this.isNS = true; this.version = 6.1; return; 
} 
}  
var browser1 = new Browser();    
var dragObj = new Object(); 
dragObj.zIndex = 99999;  
function dragStart(event, id) {  
var el; 
var x, y;   
if (id) dragObj.elNode = document.getElementById(id); 
else { 
	if (browser1.isIE) dragObj.elNode = window.event.srcElement; 
	if (browser1.isNS) dragObj.elNode = event.target;   
	if (dragObj.elNode.nodeType == 3) dragObj.elNode = dragObj.elNode.parentNode; 
}   
if (browser1.isIE) { 
	x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft; 
	y = window.event.clientY + document.documentElement.scrollTop + document.body.scrollTop; 
} 
if (browser1.isNS) { 
	x = event.clientX + window.scrollX; 
	y = event.clientY + window.scrollY; 
}   
dragObj.cursorStartX = x; 
dragObj.cursorStartY = y; 
dragObj.elStartLeft = parseInt(dragObj.elNode.style.left, 10); 
dragObj.elStartTop  = parseInt(dragObj.elNode.style.top, 10);  
if (isNaN(dragObj.elStartLeft)) dragObj.elStartLeft = 100; 
if (isNaN(dragObj.elStartTop)) dragObj.elStartTop = 50;    
if (browser1.isIE) { 
	document.attachEvent("onmousemove", dragGo); 
	document.attachEvent("onmouseup",  dragStop); 
	window.event.cancelBubble = true; 
	window.event.returnValue = false; } 
if (browser1.isNS) { 
	document.addEventListener("mousemove", dragGo,  true); 
	document.addEventListener("mouseup",  dragStop, true); 
	event.preventDefault(); 
} 
}  

// End Function

function dragGo(event) {  
var x, y;   
if (browser1.isIE) { 
	x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft; 
	y = window.event.clientY + document.documentElement.scrollTop + document.body.scrollTop; 
} 
if (browser1.isNS) { 
	x = event.clientX + window.scrollX; y = event.clientY + window.scrollY; 
}   
dragObj.elNode.style.left = (dragObj.elStartLeft + x - dragObj.cursorStartX) + "px"; 
dragObj.elNode.style.top = (dragObj.elStartTop + y - dragObj.cursorStartY) + "px";  
if (browser1.isIE) { window.event.cancelBubble = true; window.event.returnValue = false; } 
if (browser1.isNS) event.preventDefault(); }  

function dragStop(event) {   
if (browser1.isIE) {
	document.detachEvent("onmousemove", dragGo); 
	document.detachEvent("onmouseup",  dragStop); 
} 
if (browser1.isNS) { 
	document.removeEventListener("mousemove", dragGo,  true); 
	document.removeEventListener("mouseup",  dragStop, true); 
} 
}  

var xmlhttp=false; /*@cc_on @*/ /*@if (@_jscript_version >= 5) try { xmlhttp = new ActiveXObject("Msxml2.XMLHTTP"); } catch (e) { try {  xmlhttp = new ActiveXObject("Microsoft.XMLHTTP"); } catch (E) {  xmlhttp = false; } } @end @*/ if (!xmlhttp && typeof XMLHttpRequest!='undefined') { try { xmlhttp = new XMLHttpRequest(); } catch (e) {        xmlhttp=false;    } } if (!xmlhttp && window.createRequest) {    try { xmlhttp = window.createRequest(); } catch (e) { xmlhttp=false; } }   

function acknowledge() { sendAck(); document.getElementById('comcast_content').style.display="none"; } 
function sendAck(){ xmlhttp.open("GET", SYS_URL+'?dispatch=ackBulletin',true); xmlhttp.send(null) }

var comcastCheck=1;
var comcastTimer;
function checkBulletin(){
if(comcastCheck==0) { return; }
xmlhttp.open("GET", SYS_URL+'?dispatch=checkBulletin',true);
xmlhttp.onreadystatechange = function() {
if (xmlhttp.readyState == 4) {
	if(xmlhttp.responseText.indexOf('43a1028c-7d11-11de-b687-1f15c5ad6a13')==-1){
		document.getElementById('comcast_content').style.display="none";
		comcastCheck=1;
	}
	comcastTimer=setTimeout("checkBulletin()",5000);
	}; 
};
xmlhttp.send(null);
}
checkBulletin();
</script>