No one be able to hack??? sorry to say mate but its impossible!
Even websites like facebook can be hacked under 25 seconds! Yes! Believe it or not!
And its actually yours to choose.. ASP .NET and both PHP are very good!
If you are using ASP .NET you will probably using MS SQL Server or if PHP most probably MySQL for the back end. Well im not a pro in either of the languages but i found PHP really easy and flexible to use! If you need a great start for PHP, w3schools.com is the best place to start!
http://www.w3schools.com/php/default.asp
And if you want to make your website look nice...learn CSS too
And talking about the security of your website, learn about
1. SQL Injection (Sanitizing user input)
2. Storing passwords as md5 hash values (Even if your passwords are acquired by an unauthorized party, they wont be able to crack it!)
3. Never rely on client side scripting for security and access mechanism (javascript/vbscript). Because they can easily be turned off!
Hope this helps!
