HTML controls may not be browser independent but web
controls are always browser independent.

HTML controls have not need to write runat="server" means 
it  not send request to server for any evant when in web 
server control every time send request to server.

--Web server Control
 Web server controls are just like HTML controls... 
only different. Let me clarify that. 
Web controls are easily identified by the fact that they 
have a
 runat="server" attribute. They are also handled at the 
server by
 the ASP.NET runtime when a page containing them is 
requested. 
They can expose and raise server events which you can use 
to 
interact with them. They are identified by giving them an 
id 
attribute which you can then use to reference the control 
in 
your code. In all these ways, web controls are just like 
HTML
 controls.

--HTML Controls

The HTML controls might feel slightly quirky if you are
 used to forms based development with Microsoft tools. For
 instance, HTML controls have no direct properties 
available 
to set the colors or font used by the control when it 
renders.
 Another example is the Value property exposed by the 
HtmlInputText
 field. We generally expect a text box control to have a 
Text property
 for us to get or set the string to display. 

In this sense, HTML controls remain true to their roots and 
are 
not far removed from writing just HTML. If we want to set 
colors 
or font information – we can use the Attributes property. 
The Attributes property represents all the name / value 
pairs in 
the HTML element for the control. For example, a control 
might have
 an attribute “class” which will assign the cascading style 
sheet
 class. In the example above, we are assigning some inline 
style
 information to the style attribute of the control. On the 
client
 this attribute will render inline with the element.