The term 'Client-Side' refers to the fact that these are languages that process locally inside your browser, as opposed to 'Server-Side' languages that 'run' or process at the web-server (which we covered in our last post).
These are the most frequently used client-side languages in use across modern web browsers (Chrome, FireFox, Internet Explorer, Safari & Opera).
DHTML (Dynamic HyperText Markup Language)
It's important to differentiate here that 'dynamic' in this sense still means client-side processing of a page, and not dynamic page creation, which happens server-side via languages such as PHP or ASP.
Nowadays, a 'dynamic' webpage usually means it's utilising PHP or ASP, together with a database connection, to create the page at the server. A good example would be Amazon.com. Amazon has over half a billion pages, but these are not stored as individual web pages; each page is created 'on-the-fly' by a program script that pulls information from a massive database, and then layers it into template pages.
This way, whenever the database is updated (product information, pricing and user-comments for example,) the web page always shows the latest information. It would be a virtual impossibility for Amazon to maintain half a billion individual web pages as static HTML - and incredibly inefficient; not to mention the fact that it would remove most of the social/feedback/interactive elements of the site.
Java was originally designed as a platform-independent programming language to be used in consumer electronics, and has a number of features which make it particularly useful for the web.
Unlike most full programming languages, Java is not compiled into a platform-dependent machine code executable file, but is instead compiled into a special platform-independent Java executable - which is interpreted by a local Java runtime environment. It is essentially the responsibility of the user to have a JRE (Java Run-time Environment) installed so that they may use the Java application.
Side-Note: Java is now owned by Oracle after being purchased from Sun Microsystems in 2009. It is believed that Oracle purchased Sun and Java as more of a strategic move, so that they could own the environment in which much of their software is written, and become more of an integrated supplier of hardware and systems. Oracle also own MySQL.
In many ways, Ajax has opened the door to a whole new world of exciting possibilities. Because of this, Ajax is becoming more and more prevalent on websites, as fast dynamic data look-up becomes vital to socially-driven sites. And the really big advantage is that the vast majority of browsers will support it as standard – without extra plugins like Adobe Flash etc.
VBScript (Visual Basic Script)
VBScript is based on Microsoft's Visual Basic programming language, although it is simpler to use. VBScript is also the standard default language for ASP.NET (Active Server Pages) - and this remains its main use today; as this is server-side, rather than client-side.