When you first visit LastCalc you'll see the Help Panel on the right of the page. This help is generated from a single HTML file help.html by Help.java.
The cleverest thing about this mechanism is that it automatically does math for you, so in help.html you can just type:
By the time the user sees this, the appropriate answer will be appended to it. This works for variable and function definitions too.
Internal documentation for LastCalc.com