Hi Poonam,
 Pls. visit the following links for the answers..
and one more poonam, before posting these type of common
questions first search for the keywords in the site once using
search utility provided at the home page of allinterview.com.if
u didn't found what ur searching thru that , then only post it..

http://www.allinterview.com/showanswers/1619

http://www.allinterview.com/showanswers/3875

Thanks

Severity:Seriousness of defect wrt functionality.
     High: If without resolving the testing,we r not able 
to continue testing
     Medium:Compulsory to solve at one or the other stage 
but able to continue testing
     High: May or may not resolve

Priority:Importance of defect wrt to customer
(High,Medium,Low)


Plz let me know if it's wrong.

Low Severity and High Priority:

When there is a spelling mistake in a Login page i.e for 
example The company logos such as SATYAM is spelled as 
SAYAM in the front page of the application. This is treated 
as a Low severity and High priority.
(or)

Banking application:
in some situations customer will not get confirmation 
message even though the process is going on smoothly at 
backend.

Medium Sev and Medium Priority:

When there are mistakes in Error messages or warning 
messages.

High severity and Low priority:

Suppose as per clients req ur application should work on 
Both IE 5.5 and IE 6.0. But it is working fine with IE 6.0 
and not working with IE 5.5.
Hence it is not meeting the req it is high sev and hence 
it's functionality is working fine but can fix it at any 
time so of low priority.

Swetha, answers given by you are correct, but Severity and
Priority are reversed here.

Severity means: Seriousness of defect wrt Customer.

Priority: Importance of defect wrt to Functionality