Some Information About HTML & CSS

HTML is supported by all web browsers (by definition), and CSS is supported by most relatively recent versions of browsers.

Client-Side Scripts:

"Scripts" is a general programming term for short, text-based software programs. Client-side scripts are embedded in HTML web pages, which execute within the viewer's web browser software (i.e. they execute on the "client" side of the client/server web architecture, rather than on the web server).

These scripts can be used to do simple computations, verify data, display calculated information on a page, respond to the user's mouse motion and mouse clicks, put new browser windows on the screen, show and hide text and images, change text styles, and create drop-down menus and similar effects. Client-side scripting languages do not have the complete functionality that would be available in a full-fledged programming language (such as C or Java), and for security reasons, are limited to doing calculations and actions based on the content, markup, and embedded data from the HTML page they are in, along with information entered by the user in forms on that page, and reactions to things the user does in the browser window (such as moving the mouse).

The most commonly-used client-side scripting language is JavaScript, which is supported on most relatively recent browsers; unfortunately, each browser has its own variation of JavaScript, as there are not any real standards for the language. Other client-side scripting languages, which are supported only by a limited number of browsers, include VBScript and JScript. Typically, a software developer is needed to write client-side scripts, but many pre-written scripts can be purchased or downloaded, for use and modification by less technical web designers.

Browser Plug-Ins:

Browser plug-ins are programs a user can download, which run inside a web browser window and add functionality to the browser -- that is, they allow the browser to display non-HTML content, and interact with the user in ways that go beyond client-side scripting. In some cases, the plug-in enables content to be displayed inside an HTML page; in other cases, the plug-in takes up the whole browser window. Generally, once the user has downloaded a plug-in for their browser, whenever the browser encounters content that corresponds to the plug-in, it automatically displays it in the current browser window.

Creating a plug-in program requires significant software development expertise and time, and each type of browser, on each operating system, requires a separate plug-in to be developed. For that reason, most web designers and developers will not develop their own plug-in software, but instead may develop content that can be displayed using existing plug-ins (such as Flash Action Scripts, MPG movies, and PDF files). Software development expertise is also necessary to create complex Flash scripts and Java applets.