Answer: A theme contains one or more skin files. A skin is simply a text file with a .skin extension. It contains definition of styles applied to server controls in an ASP.NET page.
For Example:
<asp:button runat="server" BackColor="blue" BorderColor="Gray" Font-Bold ="true" ForeColor="white"/>
Defines a skin that will be applied to all buttons throughout to give it a consistent look and feel.
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