For some time, various Web Kit enabled browsers have supported background gradient styling, but it’s only really since the widespread use of CSS3 (and at the same time, the release of IE 9), that mainstream developers have been utilising them.
Because like with all emerging technologies there were early adopters of the method, there are a few legacy properties that still need to be defined to ensure maximum coverage amongst the modern browsers. Therefore to ensure that the majority of your users are able to view the background, you should declare 6 different properties in your style sheet for each element .