That's not always true. Any image with an alpha channel will have an opacity style attribute. In the firefox logo[1], for example, you see things like this: <td

That's not always true. Any image with an alpha channel will have an opacity style attribute. In the firefox logo[1], for example, you see things like this: <td bgcolor="#081b3c" style=opacity:0.17;filter:alpha(opacity=17) />. [1] http://www.imgtocss.com/convert?url=http://www.imgtocss.com/assets/images/firefox.png http://www.imgtocss.com/convert?url=http://www.imgtocss.com/...