Is it possible to use different technologies in one website
Phisical architecture of web application can be different from the logical one visible through browser. Basically it is achieved by putting front web server (think of apache with mod_proxy, but it can be any other moder web server supporting reverse proxying) and mounting web application servers (java/python/whatever) to different paths (like /app1 for java app, /app1/subapp for python app, /app2 for php app). Of course those applications work independently by default, so if you want to pass some data between you have to establish some communication between (direct socket-to-socket or indirect with some messaging middleware or database). 
In general it is very broad topic, so if you're interested, try with some basic keywords: application servers, load balancing, reverse proxy, url rewriting.
I was watching the tutorials for python and the guy told that he coded the Address books and spell checker for yahoo mail in python.
Now initially i was thinking that if i build the website then i have to use one language either php or java or asp or anything.
But i am confused how can we make make separate modules in diff languages and combine to make one website
Any ideas