How do Web Pages Work?

When the average web user reads the news in their web browser, they may not know that a huge number of technologies requiring millions of hours of invention, development and improvement makes it possible. The average web page today includes such technologies as HTML, XML, CSS, Javascript, Flash, PHP, and sometimes Perl, Python and often an SQL database. What is all that stuff anyway?

HTML and XML are both "markup" languages. A markup language is simply a mechanism by which certain instructions are attached to words and illustrations to explain how they should be presented. Web browsers read markup languages like HTML and then generate a display of the data based on the instructions contained in the HTML.

HTML stands for "HyperText Markup Language." XML stands for "eXtensible Markup Language." The difference between the two is that XML can be written with custom instructions while HTML is more standardized with a pre-selected list of available instructions.

Recently, web developers have found it easier to produce pages where the data and the presentation are seperated, making improvements much easier. One of the technologies that makes this possible is called CSS or "Cascading Style Sheets." CSS allows developers to change how a page looks without changing any of the information on that page.

Javascript is an actual programming language, although Javascript is interpreted instead of compiled into a binary program. In Javascript, developers can perform mathematical calculations, evaluate decision trees and check user input for errors. Javascript is a client-side language, meaning it is most useful processing information in the web page itself, such as the data entered into a form.

Flash is quite a bit more complex than Javascript. It is also a programming language of sorts, containing a language called "Actionscript." Flash is also a multimedia presentation system, allowing developers to construct animations including sound, music and even video. Flash is installed on most new computers and is included with most web browsers.

PHP is an interpreted programming language similar to Javascript but also distantly similar to a markup language, since PHP can be written directly into the text of a web page, while Javascript is usually seperated into script blocks. PHP is widely used by web developers because of its utility when combined with databases.

Perl (PERL) is an acronym which stands for Practical Extraction and Reporting Language. It is also an interpreted language like Javascript, except that Perl, and Python as well, both run on a web server instead of the client. Perl and Python are both extraordinarily powerful languages for interpreting and searching text data, which explains their usefulness in a medium like the web which consists largely of text. Many web servers have similar programming languages called "shell interpreters" which have some of the same functions.

SQL stands for Structured Query Language. It is a standard language used by databases to search, sort and interpret data stored in database formats like records and fields. SQL is distantly similar to the syntax of spoken language, and is extremely powerful especially when combined with relational databases like many of the modern systems used on web servers.