there are several ways to send sms from WEB SERVER. here i am explaining about simple http method.
steps needed to send sms via your web page
1.create an account in your prefered gateway
2. if you want you can code by your self or use the sms packages
3. and put those code in your server with your user name and password and execute it
it's work well for me..you too can try. if you have doubt then ping me at:email@example.com