Client-side scripting is based on the idea that the computer which the client
is using to browse the web has quite a lot of CPU power that can be used to
interpret logical instructions as well as render HTML, for example, such tasks
as form input validation might be accomplished on the client side without a
roundtrip to the server. Hence, it makes sense to share some of that burden
between the client's machine and server by reducing some of the processing by
the server and giving it to the client's machine.
Client-side script is delineated by the <SCRIPT> and </SCRIPT> tags. The browser invokes the language's compiler or interpreter. Client-side script typically responds to input from the browser's user.
Client-side script is great for image manipulation, form field validation, and non mission critical functions. The disadvantage is that different visitors have their computers configured differently and use different browsers so the results of the scripting can vary. Visitor's can even turn their browser's scripting engines off.
All activity which occurs with client-side script is unavailable to the server unless the visitor submits the information to the server via a form for example. Conversely, Server-side scripting is always available to the server and as a result, it will produce results that are more consistent with database connectivity.
Therefore, lets move on to Server Side Scripting