The Authentication Types are: 1. BASIC Authentication. 2. DIGEST Authentication. 3. CLIENT-CERT Authentication. 4. FORM Authentication.
the BASIC Authentication features are: 1. easy to use. 2. it is supported by all of the Browsers. the disadvantages of BASIC Authentication are: 1. not scure becaue the password transfered in clear text (not encrypted) 2. you can not customize the look and feel for this method.
the DIGEST Authentication features are: 1. it is similar to the BASIC Authentication but the password transfered in encrypted mode. the disadvantages: 1. it is not supported by all the Browsers. 2. it is not supported by all the Web Containers.
the CLIENT-CERT features: 1. it is the most secure method. the disadvantages 1. it is expensive to implement becuase it needs a certificate from CA (e.g., Verisign)
the FORM based features: 1. easy to use 2. the look and feel can be customized. the disadvantages 1. it is not secure. 2. need the session to be enabled.