I have followed this link

"http://www.liferay.com/community/wiki/-/wiki/Main/Development+Environment+%28Windows%29#section-Development+Environment+_28Windows_29-LiferayInANutshell"
to setup the liferay source code development environment.
After running " ant clean start build-ext " command my build is failed by showing "Target "build-ext" does not exist in the project "portal"" this message.

Thanks
Ponnivalavan

Just do a
ant start
ant deploy

I'm guessing you're using Liferay Portal 6.0.

It looks like that wiki page was written for version 4.3 (although it mostly applies for 5.1 and 5.2 also). Basically, the Ext environment was removed in 6.0 and replaced with an Ext Plugin. The Ext Plugin has a much smaller footprint and gives you more more options to customize the portal. Take a look at the official docs for instructions on installing and using an Ext plugin

Samuel's response is right if you just want to build a ext plugin. I was answering in my own context of building Liferay. Doing a ant deploy would actually deploy Liferay on to an application server.