header background image mo work in css code example
Example 1: background isn't working if in separate css file
background-image: url(../picture-folder/your-picture.png) 0 0;
//No quotes, two dots before "/"
//Also make sure that your <img> in html has some transparent image as src
Example 2: background-image url not working
background-image: url(nickcage.jpg); // No quotes around the file name so just write it down without "nickcage".jpg