Frameworks
There are frameworks you can use today that comes in as a lightweight yet highly efficient Ajax based framework. However, once you have started using this particular framework things might not be as powerful as they are. They are able to solve your cross browser problems but eventually some functions are a little bit harder to implement.
In the end, you end up developing an Ajax based widget instead of a full blown application. Its quiet frustrating since most of the lightweight frameworks could tell you straight in the face that they can easily build an application but nothing happens as you continue using the framework.
On the other hand, here is Clean (actual framework name) Ajax. Clean is another lightweight technology wherein you might end up developing a widget. But Clean Ajax framework has clearly indicated that they are not, above all things, a widget-only application.
In gist, Clean Ajax is a framework that could be easily infused in DHTML coded websites. With the addition of Ajax, you will eventually have a good looking website. Since it is lightweight, it can be easily infused to your website and your site is ready in no time.
One of the best features of this framework is that its server-side agnostic. That means any language you are implementing in your server should be handled just well by this framework. As long as the DHTML side is properly coded, the server could be easily implemented with this framework.
The reason for being server-side agnostic is because it is lightweight. Some may think that the application have too much coding since it has configured every server language and translate it to Ajax, but it is actually simpler to be agnostic than to concentrate on a language. Clean Ajax was derived from a Java-based messaging API and they have developed it into a full blown application. Now you know why you will not end up developing another widget since Clean Ajax was developed from one.
Lastly, just like any Ajax based application; Clean Ajax builds a JavaScript server-side. Instead of learning JavaScript for Ajax, you just have to learn Java and eventually move one to build an Ajax based application because of its close association with JavaScript. Being a messaging application is also an advantage because data transmission is easy. Whether JSON or XML, the mark-up language should be no problem for building an Ajax based application.
A loot at its source code, reveals a stripped down framework that leaves only the bare essentials. Since its server-side agnostic, the options are endless when you are considering a mash-up of the application using Clean Ajax. That way, you will be able to build a good looking website with the use of other frameworks and the essentials with the use of Clean Ajax. DHTML makes the over-all look of your application really light while maintaining the functionality you need from Clean Ajax. The combination of DHTML and Ajax is great and Clean Ajax exploited that harmony to build a good framework.