I am new to html and have many questions, but right now i am designing a website header and want to make it so that it expands to fit the browser when fully open, and also looks ok when only a small window is open. Ideally i'm going to have an image on the left hand side and another image on the right hand side of the header. Maybe just a solid colour running through the center. Any ideas??

If you're not familiar with CSS you might use a 100% wide, three-column table.

If you're familiar with CSS you can use two images floated left and right. The space in between can be a tiled background-image or a solid color. If you don't have any real header text, put the images in a H1 element as their container and use a suitable image ALT text. Give the H1 the same height as the images or add a clear after the images.

Thanks for the quick response. I'll have a go with your ideas.