Internet Explorer 8 introduced a new mechanism for ensuring backwards compatibility with websites built for IE7, so "the web" didn't break with IE8's more standards compliant rendering. You could tell IE8 to render your website as IE7 and therefore avoid having to fix potential problems with markup or stylesheets. You can do that in two different ways:

Using a meta-tag:
<meta http-equiv="X-UA-Compatible" content="IE=7" />

or this HTTP header:
X-UA-Compatible: IE=7

This puts IE8 into IE7 rendering mode. You can read more about how and why this was done and made into a standard at A List Apart.

The bonus feature

When IE8 renders a page, it looks for the meta tag or HTTP header in order to determine  whether or  not to render in regular standards mode or IE7 standards mode. So you would think that if you don't add the meta-tag or HTTP header, IE8 will just automatically render in IE8 standards mode, right?

According to this flow diagram on IE8 rendering, this isn't the case. If you don't specify any meta-tag or HTTP-header, IE8 will go through a lot of checks in order to determine how to render your webpage. You can very easily avoid the overhead and uncertainty by specifying to always use IE8 rendering mode.  The diagram tells us to use the meta-tag to specify this directly:

<meta http-equiv="X-UA-Compatible" content="IE=8" />

This meta-tag tells IE8 to skip directly to the DOCTYPE check by bypassing all other checks. If you can't add the meta-tag but can add an HTTP header, use this:

X-UA-Compatible: IE=8

The diagram tells us that the meta-tag is preferable over the HTTP header.

Always target the latest IE browser

Setting the X-UA-Compatible meta-tag/header to IE=8 only targets IE8 and no other browser. But what happens when IE9 ships? Microsoft has been clever enough to support the latest IE browser no matter what version might be. You can set X-UA-Compatible to IE=Edge and it will have effect on IE8 and all future IE versions. Keep in mind that upcoming beta releases and internal builds might not renders correctly, so use the IE=Edge at your own risk.

Button disappears

Another nice thing about directly specifying IE8 rendering mode is that the Compatibility View button disappears from the toolbar. Removing that choice might tell some visitors that what they are seeing is actually how you meant for your webpage to look.

This is one of those little features that gives you a little extra control without compromising anything. I see no reason not to use this on any IE8 standards compliant website today.

Last week a colleague and I gave a talk about scalable architecture and where my colleague talked about databases and application layer scaling, I talked about scaling websites. More precisely, we talked about the upcoming ZYB/Vodafone project. 

Since there’s still a lot of secrecy about the project, we managed to keep the concepts general. General or not, I’d like to share some thoughts on a different way of scaling websites.

Load balancing

Larger websites are often hosted on multiple web servers under a load balancer that distributes the requests evenly among the servers. This is an old technique for scaling out websites and has been widely used as the de facto scaling mechanism for years.  It’s good, it works and it’s cheap. It’s cheap because web servers often don’t have to be the biggest machines in contrast to e.g. database servers.

So, a load balanced web server setup provides good and cheap scaling possibilities.

Reversed load balancing

Any website, load balanced or not, can also use the vast untapped resources in the visitor’s browsers. Think about it. Quad core CPU’s and 4GB memory is almost standard today – even on laptops. Why not utilize the machine power behind the browsers to do some of the scaling for us?

Traditionally, this is done using browser plug-ins like applets, Flash and Silverlight, but many more sites use JavaScript. Modern browsers process JavaScript very fast and efficient which makes it possible to use JavaScript for scaling purposes.

To utilize the browsers memory we can cache data in JavaScript so we can eliminate chatty communication with the web server. An example would be to load all the data needed behind the scenes after the page is loaded and store it in JavaScript variables.  To utilize the CPU we can make calculations, dynamic rendering and other logic in JavaScript as well.

By pushing some of the load to the browser we are able to scale even more than just using regular load balancing.

It’s not for everyone

There are some problems with this approach that makes it a bad choice for some websites. If enough of the visitors are using old browsers like IE6 then they will get a worse experience because JavaScript runs too slow. There’s also the case where a website just doesn’t have any data to cache like a personal website.

For other types of websites it makes perfect sense. If your visitors have modern browsers and your website is heavily data driven, then it’s a possible candidate. The tests we have done at ZYB shows huge benefits by loading data behind the scenes - both the performance and scalability improves significantly. The load on the web servers dropped drastically with this technique. I hope to be able to show you some real numbers later.