Rendering of HTML elements..

Java components are independent of the platform since the VM takes care of interpreting the byte code and executing the machine specific instructions. But there is a separate VM coded for each platform. The logic is similar with browsers... the browser interprets the HTML tags and renders the UI based on those. Each browser is coded for the particular environment with the rendering behaviour compliant to a defined set of rules / specifications. Of course, there are subtle differences in the way different browsers behave. :)