For those of you using Fiddler HTTP Debugger (which is a great tool I've blogged about many times in the past,) there appears to be an issue when using IP addresses. This is especially noticable when using private subnet IP addresses (such as 192.168.1.*.)
The problem I was seeing was that requests to my developer server came to a crawl when using Fiddler. Speed to external domains was working fine. If I turned off capturing, speed resumed. I finally was able to figure out that by setting up a DNS entry, speed would resume.
Since this was slowing me down, I sent Eric Law, the developer of Fiddler, an e-mail message reporting the problem. He was very quick in researching the problem.
Ok, so the title is misleading. CF doesn't really have a concept of null, but it does have the concept of "not exists."
If you need to differentiate between when an argument of a function has been supplied or not, set the required attribute to true and leave the default attribute off. If the argument is not supplied to the function, then a against structKeyExists(arguments, "argumentName") will return false. If a value has been supplied, the function will return true.
Here's an example: