What is the difference between CSSClass and class property of controls?

Answer:

Both are used for applying css classes to the controls but there is only one difference between both.
As we can write either CSSClass or class property for server side controls i.e. Asp.net controls but only use class property for HTML control.

For Example:-

<input type="button" id="btn1" value="Click Me" class="font_bold"/>        

<asp:Button ID="btn2" runat="server" Text="Click Me" class="font_bold"/>

<asp:Button ID="btn3" runat="server" Text="Click Me" CssClass="font_bold"/>