Usability Testing:
                   Usability testing comes under system
testing.Here mainly testers are concentrating on whether
there is user-friendlyness in the build or nor?
It classified in to 2 types
1.User Interface Testing:
                         Here testers concentrates on
whether there is look&feel,ease of use in all the screens of
the application build?

2.Manual Support Testing:
                         Here testers concentrates on
correctness and completeness of help documents in the build.


Compatability Testing:
                       Testers validates whether the build
is working under all the customer expected platforms

Hai

Usability testing means :here the testers test  whether the 
app is user frindly or not.
EX:yahoo is better than rediff mail

Usability: 
Testing the "user friendliness" of the software

Compatibility Testing:
Testing how well software performs in a particular
hardware/software/operating system/network/etc. environment.

Prabhu Subramanian
CSS India Pvt. Ltd.

Usability testing:

              user friendlyness of the screen of the build
(allignment,font size,spell check, color, grammeritical 
mistakes , and image clarity & look


Compatability testing:

              The app. build is going to support customer 
side expected platforms or not

usability testing:to validate the s/w user friendly testing
compatability testing:to validate the s/w to check if the 
s/w is working different opreating syustems .