updated index.html added 'active' class to both the wrapping <LI> and it's child <A> for the Regex tab to identify it as the current active tab when the page is loaded.
updated regex.js Added heaps of comments and reformatted some existing comments. In textareaClick() simplified the assigning old attributes to new field. Tweaked functionality of showOutput() so that the output tab is the active tab and the focus is set to the output textarea field. Added new function setActiveTab() to handle switching tabs. (There is probably a jQuery equivalent to this but...). Tweaked submitTest() so that it sets the active tab to Regex.