Front-end Programming
JavaScript
Form validation, timers, counters, calculate/total data, change selections or options when something is selected or checked, autopopulate fields based on choices, show/hide blocks of HTML, etc.
Ajax
A new-ish name for technology that's been around for several years; it's an open standard using JavaScript and is supported by most browsers. I use it to create interactive web applications. With Ajax, there's no need to reload entire page - the rest of page remains available to the user while request is being made and processed.
CSS
I use CSS to set both the layout and style (colors, fonts + font sizes, rollovers, etc) on all web pages. Even if you're still laying out your websites with tables, you should use CSS for for everything else. CSS puts all the style attributes in one place for easy maintenance and updates. And because the styles are defined only one in one place, your pages are smaller and therefore load faster.
HTML
Yes. This site. And so many more, since 1995.
