JavaScript Overview by Floyd Jay Winters, State College of Florida
DHTML (Dynamic HTML) uses CSS and JavaScript to modify page elements on the fly to create interactive and animated web sites.
Cascading Style Sheets use a stylesheet language to quickly modify styles, formatting and presentation for an entire Web site, while easily bringing a consistent look and feel to a customized site.
JavaScript is a client-side scripting language and has a similar look to Java programming and CSS.

JavaScript can:
  1. Allow Interactivity
  2. Display Pop-up messages to users
  3. Perform Calculations
  4. Perform Validation
  5. Work with Event Handlers such as onload or onclick
  6. Produce and preload Roll-over images
  7. Work with Cookies
JavaScript is Case sensitive. Almost all commands are in lower case.
Internal JavaScript commands are placed inside <script> tags.
External JavaScript files have a .js extension.
External scripts are often loaded in the <head> tags.
For example: <script src="scriptName.js" type="text/javascript"></script>