Header image not showing

[wotnow]

Hi I have been playing around with all the tutorials and wiki information and have designed a header and placed it in the right folder .. have altered the logo wrapper in CSS .. and although through most of my poking and prodding it was displaying .. now it is not. Is there somewhere specific i could go to check why its not displaying?

Also if my header image is 800 x300 pixels and I want it to display right across the screen and have used background colour to fill in the white space either side - should the image not be placed in the header wrapper instead of the logo wrapper? Thanks