This is my project structure:

I am going to add css file into HeaderTester.xhtml file:
This is HeaderTester.xhtml:
<?xml version='1.0' encoding='UTF-8' ?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://xmlns.jcp.org/jsf/html"> <h:head> <title>Here is header</title> <link rel="stylesheet" type="text/css" href="headerStyle.css"/> </h:head> <h:body> This is Header tester class <div id="header"> <h3>Sajjad HTlo</h3> </div> </h:body> </html> Css File:
*{ margin: 0; padding: 0; } #header{ background-color: gray; width: 100%; height: 60px; } h1{ color: silver; } But just displays texts in result!
