Are headers generally coded from scratch or are they images, Im slowly reading css tutorials and from talking to people they say they code everything from css, but I always thought the header way an image, also say I wanted a gradient background colour its simple to do in photoshop but how would you do it in css I can only get a solid colour:

<style type="text/css">
body {background-color: yellow}
h1 {background-color: #00ff00}
h2 {background-color: transparent}
p {background-color: rgb(250,0,255)}
</style>

To get a gradient background, you can use a gradient image asthe background on the body element, and set it to repeat horizontally...

ie: background-image: url('yourbackground.gif');
background-repeat: repeat-x;

I thought it must be something like that, thanks the the help

background-image: url('yourbackground.gif');
background-repeat: repeat-x;

Or shorthand:
background: url(yourbackground.gif) repeat-x;

The quotes around the file name are not necessary.

Whether or not you use an image for a header depends on your layout, it isn't always an image at all.