'jQuery' is undefined Jquery jquery-ui-dialog

I am using jQuery.ui.dialog.js to show the modal pop up.. But this Jquery.ui.dialog.js is throwing a javas开发者_运维技巧cript error 'jQuery' is undefined. Please help . How can i resolve this. I am using this two .css and .js

1.jquery.ui.dialog.css & 1.jquery.ui.dialog.js 2.jquery-ui-1.8.2.custom.css & query-ui-1.8.2.custom.js

Please advice.

Have you ensured that your tag for jQuery comes before the same for jQuery UI?

Beginners guide is here:

http://learn.jquery.com/jquery-ui/getting-started

Make sure you have included the jquery-1.4.2.js file in your HTML.

You need to include the jQuery library itself to use jQuery UI, make sure to download and include that script as well from the jquery.com download section (also make sure it's beofre all other jQuery dependencies, plugins, UI, etc).

Or, include it from a CDN like this:

<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>