Well , cometd is not very hard to configure .. you would get examples in the comed site....
it has two methods subscribe and publish , for doing a ajax push u have to subscribe to a channel and publish the content to the channel .. thats the basic use ... we used the same methodlogy.
There are to version of cometd implementations dojo and jquery .. we used dojo's . It doesn't matter which one u use .. once u see the examples u would understand ....
This subscribe and publish methodology is good for chat applications and also broadcasting over the network ...
for website design and backend functionalities ... we used j2ee framework and jetty webserver .....
If I understand ur question correctly ... u have to install Jetty 7 ( webtide version ) .. only this version supports Cometd .... by install I mean unzip :-) .. its so easy ... in the web apps folder u get a cometd folder with examples .. understand this examples properly .. your web application's jsp pages would be using the javascripts to subscribe and publish .... now in publish function you would be calling certain javascript function, which would in turn call a "div" ... thats how u publish or broadcast ur content ....
I assume u r familiar about javascript , jsp's and servlets ...
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thanks ,
Ashok