JavaScript
Javascript and VB Script are both client side scripting engines that are interpreted on the client. Client side javascript is platform independent and much more widely used than vbscript(which is used most often used on sites developed with active server pages, a Microsoft technology). No matter what web server(i.e., Apache or IIS) and/or server side scripting engine you choose(i.e.,PHP or ASP), javascript will provide a formidable first line of defense in controlling the display of content on your web site.
Any process, property, method, or event that can be captured and handled by the browser after a page is rendered by the server shoud be delegated to javascript or alternate client side scripting engine. Functions and event handlers, which can interface the document object model api, can then implement dynamic changes to static HTML according to user input and conditions from the time the page is inititally parsed and loaded until the time a new page or form data is sent to, or received from the server. Some examples of this are page navigation, form field validation, image rollover effects and changing element styles on the fly. When data is collected on forms is posted to the server or data to refresh the page is needed from the server another scripting technology, such as PHP or ASP, will take over on the server side. Mixing client and server side scripting in a strategic manner will produce a web site that is responsive and dynamic.