Google and Facebook bypassing P3P User Privacy Settings

I wrote about P3P a very long time ago, and have implemented it on several websites. Some history, the W3C crafted the P3P policy.
Microsoft introduced P3P support in IE6 (in 2001) and it remains implemented in all current versions of the browser. The primary intended use is to block 3rd party cookies within the browser on behalf of the user.

Interesting enough, Microsoft has had been a bit of a struggle with Google and Facebook, which send the following HTTP response headers.

Google’s Response:

P3P: CP="This is not a P3P policy! See for more info."

Facebook’s response:

P3P: CP="Facebook does not have a P3P policy. Learn why here:"


HTML4 script defer

This HTML4 attribute was intended to defer/delay execution of specific javascript code until after the page is rendered. In theory, this makes the website “appear” faster as the functions relevant to the User-Interface can be executed before other “background” processes that would otherwise block the screen from displaying.

<script defer="defer" src="example.js"></script>

NOTE: Do not use defer for external scripts that might depend on each other if you need to support MSIE9 and earlier.


“msapplication-config” and browserconfig.xml

Windows-8/MSIE-11 introduced Tiles, as such server administrators may have started seeing HTTP 404 errors in their server logs as it attempts to look for a “browserconfig.xml” file at the root of a website domain. If you are inclined to use this file, you should definitely look into the documentation for how to best make use of it. Others may just wish to prevent the error from making “noise” in their log files.

To remove the error, add the following to your pages; alternately you COULD define the URL of your file as the ‘content’ attribute:

<meta name="msapplication-config" content="none" />

You can alternately place an empty /browserconfig.xml on your web server for each domain.

An common example of how to use this file is below:

<?xml version="1.0" encoding="utf-8"?>
<square70x70logo src="/mstile-70x70.png"/>
<square150x150logo src="/mstile-150x150.png"/>
<wide310x150logo src="/mstile-310x150.png"/>
<square310x310logo src="/mstile-310x310.png"/>
<TileImage src="/mstile-150x150.png" />


Skype toolbar meta tag… preventing Skype from messing up your UI

I’ve previously documented the method used to prevent IOS devices from formatting numbers.

Users on other platforms, notably Windows, have Skype installed and it too can cause some headaches with your UI as it inserts elements to decorate phone numbers.

For users that have the Skype Toolbar enabled, the following META tag will prevent it from doing a lot of damage!



HTML cleartype meta tag?

This tag allows for activation of ClearType in Mobile IE for smoothing fonts.

<!--[if IEMobile]><meta http-equiv="cleartype" content="on" /><![endif]-->

NOTE: Future use of this approach is questionable, as MSIE10 dropped support of conditional comments, and HTML5 validators (in general) do not “like” the http-equiv values as they are not standardized


HTC/.htc files

What is it? Internet Explorer 5-9 introduced behaviors. Behaviors are a way to add behaviors to XML (or HTML) elements with the use of CSS styles.

Why avoid it? The behavior attribute is only supported by Internet Explorer.

What to use instead? Use JavaScript and XML DOM (or HTML DOM) instead

MSIE 5-9 support a scripting (VBScript/JScript) technology called HTML Components (HTCs) to aid in DHTML behaviors. Support was dropped in MSIE 10, you will have to force the browser into MSIE 9 compatibility to use these.

Mozilla? it has a similar proprietary implementation.

Included CSS style:

<style type="text/css">
h1 { behavior: url( }

Inline CSS style:

<p style="behavior:url(">Hello World</p>

Apache MIME Type:

AddType text/x-component .htc


HTA/.hta files

HTA/.hta files are a technology that Microsoft implemented in it’s browsers MSIE 5-9 to support rich web applications, MSIE 10 and newer do not implement it and must be forced into MSIE 9 compatibility mode.

Most often HTA was/is used to hide the browser controls (chrome) from the user to provide dialog windows.


<meta http-equiv="x-ua-compatible" content="ie=9" />
<!-- does not work in 10 or above, so force it back down -->
<hta:application id="example"

Apache MIME Type:

AddType application/hta .hta


Google ChromeFrame

There was some debate back when this was first revealed in 2009, but the use of ChromeFrame is still relevant for some organizations that are stuck on older browsers for legacy applications.

<meta http-equiv="X-UA-Compatible" content="chrome=1" /><!-- this is for all versions of IE -->
<meta http-equiv="X-UA-Compatible" content="chrome=IE6" /><!-- this is for IE6 and lower -->
<meta http-equiv="X-UA-Compatible" content="chrome=IE7" /><!-- this is for IE7 and lower -->
<meta http-equiv="X-UA-Compatible" content="chrome=IE8" /><!-- this is for IE8 and lower -->
<meta http-equiv="X-UA-Compatible" content="chrome=IE9" /><!-- this is for IE9 and lower -->
<meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=IE6" /><!-- this is for IE9 and lower, passes Edge to others -->


  1. Installation can be done without Administrative rights on the Windows OS.
  2. Installation will append the ‘chromeframe’ version to the ‘User-Agent’ HTTP header sent by the browser to allow it to be parsed.


X-XSS-Protection HTTP Header

This HTTP Header is a feature added by MSIE8 to force it to restrict some XSS vectors that can be disabled by the user. Generally you can add it into your webserver configuration.

X-XSS-Protection: 1; mode=block


Conditional Comments cause CSS to block

Here’s an odd one…. I’ve found that if you use the common method of using Conditional Comments to separate MSIE specific CSS, you’ve likely added a performance problem without knowing it… that is, in addition to the network connection and time required for the different CSS files.

It turns out that the standard use of this approach blocks the other downloads until the main CSS is loaded.

The solution is both simple and painless to implement…. a quick solution to this is to add an empty conditional comment early on, that is, before the main content (CSS) is loaded.. This works for all approaches, such as those where comments surround the <body> or various <link>, <style> or <script> tags.

Personally, I like to do this immediately after the DOCTYPE and before the <html> tag. Additionally, since IE10 dropped support for this technique, I’ll just target IE 9 and below for any developer that comes after me.

<!DOCTYPE html>
<!--[if lte IE 9]><![endif]-->
<html lang="en">