can we implement Live chat using CI

[eluser]Sarre[/eluser]
For this you probably want to use javascript, and especially AJAX (that allows you to update a part of your page, without refreshing the whole page, so it's what you need for a chatbox)

Many javascript libraries help make your life easier when building such an application.
Mootools, JQuery, YUI, Prototype, Dojo,... are keywords you might want to try in google ;-)

You can combine this with codeigniter. Use a javascript function that updates a div with information from your database (through codeigniter-MCV), and make it work periodical (e.g. so that every 5 seconds it updates the div). Use an input-element to enter text, and use javascript to hijack the event, and instead use ajax to send the text you entered to a controller that enters it into the database.
The periodical updating div will after a few seconds show your response in that div.

This is of course a very basic chatbox method...
But questions should rather be asked on the forums/mailinglists of the javascript libraries, as they're the specialists!

If this all sounds like Chinese, go take a look at e.g. mootools.net, my personal favorite.

Greetz.