In server controls processing would be done at server side 
but in html controls would be made to client side only.

HTML controls do process on client side whereas Server 
controls run on server side.

if HTML controls do process on client side then why they 
called server control mr kailash from HAPUR(GZB)

The html controls the server is hit only on page submit.But
for server controls on every user response the server is
hit.The server controls are used in places like railway
reservation.The html control is used in places like hotel
menu card.

Sever Control internally maintain the sate(EnableViewState 
prperty) whereas HTML control  are  not having such 
property to maintain the state.

server controls run server side and html controls run 
browser side and as well as client side . the html controls 
run on server side using runat="server"

Attaching Javascript methods for Html controls is flexible 
compared to Server controls where for servercontrols we 
need to register the Javascript method to event in one of 
the events of Page Life Cycle which is a complex task.

ASP.NET Server Controls
Advantages:

1. ASP .NET Server Controls can however detect the target 
browser's capabilities and render themselves accordingly. 
No issues for compatibility issues of Browsers i.e page 
that might be used by both HTML 3.2 and HTML 4.0 browsers 
code to be written by you.
2. Newer set of controls that can be used in the same 
manner as any HTMl control like Calender controls. (No need 
of Activex Control for doing this which would then bring up 
issues of Browser compatibility).
3. Processing would be done at the server side. In built 
functionality to check for few values(with Validation 
controls) so no need to choose between scripting language 
which would be incompatible with few browsers.
4. ASP .NET Server Controls have an object model different 
from the traditional HTML and even provide a set of 
properties and methods that can change the outlook and 
behavior of the controls.
5. ASP .NET Server Controls have higher level of 
abstraction. An output of an ASP .NET server control can be 
the result of many HTML tags that combine together to 
produce that control and its events.

 
Disadvantages:

1. The control of the code is inbuilt with the web server 
controls so you have no much of direct control on these 
controls
2. Migration of ASP to any ASP.NET application is 
difficult. Its equivalent to rewriting your new application 
HTML Server Controls
Advantages:

1. The HTML Server Controls follow the HTML-centric object 
model. Model similar to  HTML
2. Here the controls can be made to interact with Client 
side scripting. Processing would be done at client as well 
as server depending on your code. 
3. Migration of the ASP project thought not very easy can 
be done by giving each intrinsic HTML control a runat = 
server to make it HTML Server side control.
4. The HTML Server Controls have no mechanism of 
identifying the capabilities of the client browser 
accessing the current page.
5. A HTML Server Control has similar abstraction with its 
corresponding HTML tag and offers no abstraction.
 
Disadvantages:
1. You would need to code for the browser compatibility.

ASP.NET Server Controls
Advantages:

1. ASP .NET Server Controls can however detect the target 
browser's capabilities and render themselves accordingly. 
No issues for compatibility issues of Browsers i.e page 
that might be used by both HTML 3.2 and HTML 4.0 browsers 
code to be written by you.
2. Newer set of controls that can be used in the same 
manner as any HTMl control like Calender controls. (No need 
of Activex Control for doing this which would then bring up 
issues of Browser compatibility).
3. Processing would be done at the server side. In built 
functionality to check for few values(with Validation 
controls) so no need to choose between scripting language 
which would be incompatible with few browsers.
4. ASP .NET Server Controls have an object model different 
from the traditional HTML and even provide a set of 
properties and methods that can change the outlook and 
behavior of the controls.
5. ASP .NET Server Controls have higher level of 
abstraction. An output of an ASP .NET server control can be 
the result of many HTML tags that combine together to 
produce that control and its events.

 
Disadvantages:

1. The control of the code is inbuilt with the web server 
controls so you have no much of direct control on these 
controls
2. Migration of ASP to any ASP.NET application is 
difficult. Its equivalent to rewriting your new application 
HTML Server Controls
Advantages:

1. The HTML Server Controls follow the HTML-centric object 
model. Model similar to  HTML
2. Here the controls can be made to interact with Client 
side scripting. Processing would be done at client as well 
as server depending on your code. 
3. Migration of the ASP project thought not very easy can 
be done by giving each intrinsic HTML control a runat = 
server to make it HTML Server side control.
4. The HTML Server Controls have no mechanism of 
identifying the capabilities of the client browser 
accessing the current page.
5. A HTML Server Control has similar abstraction with its 
corresponding HTML tag and offers no abstraction.
 
Disadvantages:
1. You would need to code for the browser compatibility.
HTML Intrinsic Controls
Advantages:
1. Model similar to HTML
2. Here the controls can be made to interact with Client 
side scripting
 
Disadvantages:
1. You would need to code for the browser compatibility