Its very difficult to have an image resize if the image is one fixed block.
Generally, your header would include Logo set to say the left hand side, fixed using css. Then an overlay of html code to display login register, etc using again css positioning.
read this article:
http://www.1-script.com/forums/resiz...--2.htm#137708
or this:
http://www.webreference.com/programm...script/images/
getting css to do this may be possible:
http://www.bigbaer.com/css_tutorials...l.tutorial.htm