There are a few methods available to create transparent backgrounds in your pages. These methods all have tradeoffs of course.
My preferred approach is using rgba color. That’s Red-Green-Blue-Alpha. The alpha channel defines transparency. For example
In the above example, we declare a white background at one-half transparency. The disadvantage to this approach is that IE6-8 won’t recognize it, so you need to declare a background color for IE that isn’t transparent.
IE will display a white background because it does not recognize rgba() as a color definition, so it ignores this declaration. Modern browsers will use the rgba() color definition.