Jake Morgan has submitted a great article to Codeproject.com on the creation and use of an ASP.NET Dynamic Gradient Handler. We use this on our own site to dynamically create and adjust the background.
From the article:
Gradients are an essential tool for any serious graphic designer. Disciplined use of gradients can provide a simple professional touch to virtually any graphical layout. However, HTML and CSS provide no intrinsic support for gradients. Generally a tool such as Photoshop is used to save a static image file that is then tiled as a background. While this approach is effective, it can be tedious and inflexible because it requires an additional tool to manage the images. The GradientHandler can eliminate needless steps when dealing with simple linear gradients. Gradients are defined with URL parameters leading to a much more manageable code base.
Visit codeproject.com for the full article with sample code. A demonstration page for the gradient handler concept is active on elsitech.com.