Dialog windows are a great way to show quick information to your users, and to also alert them of errors, warnings, prompts for information and more. When you bring jQuery into the mix, you know you’re going to end up with a slick dialog that really makes the application or website come alive. The following is a list of 10 jQuery Alert Windows and Prompts. Enjoy!
1. Apprise
It is a very simple, fast, attractive, and unobtrusive way to communicate with your users. Also, this gives you complete control over style, content, position, and functionality. Apprise is, more or less, for the developer who wants an attractive alert or dialog box without having to download a massive UI framework. 
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2. jReject: jQuery Browser Rejection
Provides a simple, robjust, light-weight way to display rejections based on a the browser, specific browser version, specific platforms, or rendering engine. 
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3. jQuery MSG Plugin
Back in the old days we use‘alert(‘blah blah’);’ to show users a message or a warning. It is functionable but not pretty. So I used to use BlockUI instead.Later on I found out I don’t need all the features it has and I want it to beeasiler to customize. So I write my own simpler version called MSG.It can only block the whole window, it has theme suuport, afterBlock and beforeUnblockevent, … etc, and it’s only 4 kb uncompressed with code comments. 
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4. Subscriber Traffic Pop
It is the hottest new way to gain newsletter, email list subscribers in high volume with no work. The revolutionary Traffic Pop idea has been extended into a whole new category with email subscriptions! More emails = more traffic = more $$$$! 
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5. WowWindow Plugin
It is an alternative to Lightbox, for jQuery, that is much more fun and powerful. This modal window script uses CSS3 transformations to display the window, but will acceptably degrade to a workable window for browsers that do not support this. If you’re looking for alternatives to Lightbox, this may be the perfect script for you. 
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6. jQuery-toastmessage-plugin
It is a JQuery plugin which provides android-like notification messages. It’s a quite nice way to report info or error to the user. 
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7. jPopIt Plugin
Allows you to pop up a simple and unobtrusive message to a user on your website. 
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8. Freeow!
It is a plugin for making Growl-like alerts or message boxes on your website. You can customize the look and animation of Freeow! each time a message box appears, and you can alter other options such as whether or not to have the message box hide itself automatically. 
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9. SimpleModal
It is a lightweight jQuery plugin which provides a powerful interface for modal dialog development. Think of it as a modal dialog framework. 
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10. jQuery Confirm Plugin
This plugin displays a confirmation message in place before doing an action. It does not require adding any extra code apart from a call to the plugin itself. 
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http://www.jquery4u.com/plugins/10-jquery-alert-windows-prompts/