security testing like entering the password in a maskable 
way and making a password in a encryption and decryption 
format to avoid hacking which is done by the developers

Generally we do security testing like entering the password 
in a maskable way and making a password in a encryption and 
decryption format to avoid hacking which is done by the 
developer
and also we can do security testing by sql injection and
using tools like 
achillies
tamper ie
etc

We will check following things,
1.Authorization
2.Access control
3.Encryption/Decryption
In this way testing security for the web application.

thats what iam saing using third party tools like
tamper ie
achillies   etc
using this tools we will do security testing by 
implementing sql injection on to it 
ok

I we can also test it by cookies - as some systems are 
cookies dependent - and user enter the password or any or 
the secure matter - it should come in encrypted form in the 
cookies .