Background color of textbox on focus

1. Open Visual Studio
2. Create a New Website
3. Add web page

4. from WEbsite - >Add New Item -> StyleSheet- > Click Add.

5. Write code in the css file

.txt

{

}

.txt:focus

{

    background-color:Red;

}

6. Add css to the web page's head section.

<link rel="stylesheet" type="text/css" href="Styles/Site.css" />

7. Add TextBox to a web page.

  <asp:TextBox ID="txt1" runat="server" CssClass="txt" ></asp:TextBox>

8. Click F5