Using cascading style sheets, I can can modify the presentation of any part of a site by updating a single style sheet.  This example uses JavaScript and CSS. Choose a new style!:

default beige olive vivid flower

Flash movie or tutorial.

JavaScript random life insurance calculator or entry prompts.

Active Server Page in the .Net framework, calendar calculator.

By capturing "cookies" with PHP, this example shows you have entered or refreshed this page 0 times since opening the browser session. Refresh browser to see incremental count.