I wanted to create subdomains for all the categories listed here. It was not possible with shared hosting with previous web hosting provider. So, I moved to media temple and they support wildcard subdomain.
So, today I generated all the subdomains to test with all the categories here: http://learntipsandtricks.com/categories
But all of them were displaying homepage content as I had not modified the .htaccess file. So I added this: