What is JavaScript?
Javascript is a scripting language that will allow you to add real programming to your webpages.

You can create small application type processes with javascript, 
like a calculator or a primitive game of some sort.
However, there are more serious uses for javascript:
Browser Detection
Detecting the browser used by a visitor at your page.
 Depending on the browser, another page specifically designed for that browser can then be loaded. 
Cookies 
Storing information on the visitor's computer, 
then retrieving this information automatically next time the user visits your page.
 This technique is called "cookies". 
Control Browsers 
Opening pages in customized windows, where you specify if the browser's buttons, menu line,
 status line or whatever should be present. 
Validate Forms 
Validating inputs to fields before submitting a form.
An example would be validating the entered email address to see if it has an @ in it,
 since if not, it's not a valid address. 
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