Q: What is the practical difference between px (pixel) and em (pronounced m)? When is it best to use one over the other?
The short answer is that pixels measure dimensions relative to the screen while ems measure dimensions relative to type size.
The slightly longer answer is that pixels are the natural unit for measuring dimensions on a screen and are often used when precise design is required. Ems are the natural unit for measuring type and used when you want to allow maximum design flexibility.

Sometimes you might write an AppleScript script that looks right and that even compiles correctly but that doesn’t work right when you run it. The error message that AppleScript presents in cases like this isn’t always very helpful, but you can customize it using a ‘try’ block and catching any error that occurs at run [...]

Java has come along a long way. Many would agree with this. I did not until the Java 1.5 “Tiger” hit me. The tiger had several new features, and more importantly, it has new syntax. Six major upgrades that the tiger presents are certainly the generics, enhanced for loop, autoboxing (unboxing), improvement on Typesafe enum, [...]