Advanced & latest versions of browsers support transparent PNG by default. i.e. Internet Explorer 7, New Firefox, Safari and Opera etc. For IE 6 another version of this script works fine in which I gave you an example how to implement transparency in PNG for web pages. But what about background image and what if you have older browser like IE 5.5 etc.
its always a good practice to place CSS scripts outside the webpage and link to it. This helps in reducing size of pages and increases loading time. In CSS you can redefine tag styles. Make IDs or you can create your own class to use in the pages.