Javascript and Ajax Explained

JavaScript is an implementation of the ECMAScript language standard.It is also considered a functional programming language. JavaScript is primarily used in the form of client-side (you and your computer are the client) JavaScript, implemented as part of a web browser in order to provide enhanced user interfaces and dynamic websites. JavaScript uses syntax influenced by that of C. JavaScript copies many names and naming conventions from Java, but the two languages are otherwise unrelated and have very different semantics.

Javascript code is embedded in a web page. If it it is enabled, it will respond to your actions such as button clicks, moving from one field to another and suggesting actions while using the the page.

Forms can be validated before they are submitted which saves you time by not waiting for the page to be sent to the server, evaluated and being returned for corections. It can also be used to provide you with tools for filling out a form such as calendar icons, table lookups, explanation of items on the form.

Unfortunately the world has many people who want to abuse you and your computer. If you have javascript enabled and you go to a page composed by one of these people javascript, because it is running on your computer, can cause some problems. Security people are always wary of things that can possibly happen even though the probability is very low so they will always recomend disableing javascript.

Ajax (pronounced /ˈeɪdʒæks/; shorthand for Asynchronous JavaScript and XML)[1] is a group of interrelated web development methods used on the client-side to create interactive web applications. It depends upon Javascript being enabled.
What it provides is the presentation of a web page and depending upon choices made by the user (you) parts of the page are changed by keeping the current page intact while javascript goes out to the web to gather information and when it is found presents it on part of the page. The idea is to emulate applications that run exclusively on your computer.

In order to take advantage of the good parts of javascript and protect yourself from the possible dangers it is possible to turn Javascript on to process trusted forms and to turn it off otherwise. It is a bother created by the sick people on the web.
This is where you can find how you can turn it on or off.