Client server application is two tire architecture.witch 
contains Business layer and Presentation layer.
  

Web based application is three tire architecture.witch 
contains Business layer and Presentation layer,Environment 
layer.

Client server application: This is a single server based 
application and can be used locally... for example a 
application which calculates the goods n prices in a 
supermarket..

Web based application: This is a application that can be 
used on the internet and can be accessed thru any place... 
for example the hsbc banking website...

1. Client server applications run in a networked 
environment,and although you have two separate components 
to test ,you still have control over the client part of the 
application.

   Web applications run in a networked environment but you 
loose control over the client. Web applications are 
supposed to run on various browsers and platforms.

2. Client server software must be tested at the native 
operating system level.
    Web software gets tested higher up in the food 
chain,far away from the bowls of the operating system.

3. Instead web server software must be tested for browser 
compatibility and operating system compatibility. But also 
because so many various programming languages and scripts 
can live with in a single web page,the interaction of 
various applications must be also be tested. External  
software,such as shockwave and javascript and java and perl 
along with network connection must work together to create 
the expected result.

Clent server appln.-appln is loaded at the server.in every 
client machine,an exe is loaded to call this appln.
web based appln.-appln is loaded to the server,we have to 
call the appln through the browser......

Web base application:
                     Once deploy the application has to
server machine.  To access only support web browser in this
type of application is web application:

Testing tip for Web application:
 1. Test to check the Server side interface
 2. Test to check the client machine comparability 
 3. Test to check Client side:
               a) GUI Testing
               b) Functionality  
               c) Field validation
4. Test to check the Data integrity 
5. Test to check data base performance 
6. Test to check Client server performance 
7. Test to check the security 

Client Server Application:
          Once Deploy the application to server, then must
have installed server machine application exe to access 50%
server side and 50% to access the client side