How to find out the first name of a professor whose home page lists only first initial? This is probably a soft question. I am interested in complex analysis, and I want to ask the first name of this person, S. Ponnusamy, whose name I wish to mention in a paper.

What is the best way to go about asking such stuff?
If you are at a university that has access to MathSciNet, then you can look up any one of his publications (listed on the web page you linked to), and then click on his name to find out that his first name is Saminathan.