005.m1
Mathematica Note
Mathematica Version 5, released in the summer of 2003, has a large number of speed and memory efficiency improvements, particularly in the area of large numerical matrices. You might not think that's important for a periodic table website, but, much like advances in basic science, advances in the performance of basic components of a system often have surprising and far-reaching benefits.
Images, you see, are large numerical matrices as far as a computer is concerned, so to do any sort of image processing, you need a system able to import, store, and manipulate large matrices efficiently. And I have a lot of images on this website. With Version 5, I am able to process whole directories full of large image files in a quite reasonable length of time: See this sample under lithium for more details.

I should mention that Mathematica Version 5 is listed under boron not because it's boring, but because boron is element number 5. Any guesses where Version 6 is going to be listed?
005 Boron