In India web designing is so much popular. Not people from India even from abroad countries like Canada, UK and U.S every year provided huge work for Indian IT companies. There are many reasons why we have heavy freelancing work from abroad
We have very less cheap man over as compare to these countries. if a person working in Canada or U.S he can work on approx 16 to 18 $ per hr where as in India the hourly rate is very low and that is one of the major reason of so much work here of IT here in India.
In India we have good population Of IT professionals and that is one of the major reasons of cheap much power too
So these two factors are one of the major factors and based upon these two then IT Companies have good number of clients from abroad and These efforts provide dollars as a form of revenue to Indian government too.