It’s been a few years since I’ve met Chris Jackson, who in my humble, opinion is one of the smartest guys at Microsoft. Also known as the AppCompat guy, Chris Jackson is the primary developer for the application compatibility toolkit. While everyone else at MMS goes to lunch, we diehards sit here in a meeting room tuning in on the topic of application compatibility and how to get your company unstuck from legacy applications. He mentions that the "Law of Holes" principal (i.e. once you realize you’re in a hole, it’s time to stop digging) is the number one indicator for how successful a company can be in moving forward with Windows, Office, and Internet Explorer deployments. One of the funnier things to note during his presentation is that even today you can watch the usage of IE6 on the Internet peak from hours 8-5 in a given region, meaning many companies are still shackled by old business-critical applications that will not run on later IE versions.

Specifically, Chris mentions the two most common application compatibility issues when migrating older web applications are (1) not specifying DOCTYPE in the header, which you can test by running IE in quirks mode and (2) major and minor version number checking failure, which you can fix by editing the source code of the web page. Chris used a variety of tools to demonstrate troubleshooting of web apps, including Fiddler, but he made a special note that the new debugging tools within later versions of IE also helps tremendously.

In the end, the best policy for moving forward for integrating new technology with legacy applications is to allow for compromise- the cost for testing every application may be not worth the investment if you can decide which applications to leave behind. Motivate your IT team to move forward with application compatibility testing. Prioritize the most important apps and proactively test them first, keeping in mind that we work with compatibility to embrace the change rather than to provide a long-term fix.

And I just had to take an opportunity to get Chris to autograph my laptop after the show… =)