Generally this is no rocket science, using the CSS3 attribute “opacity”, unfortunately CSS3 is not supported by many browsers. As an alternative one could use JavaScript, which also might not work everywhere (if disabled due to security measures). So the easy way only works in the latest versions of Firefox and Opera.

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CSS (cascading style sheets) is the ultimate tool to create lean, fast, functional, SEO friendly and, though, sexy layouts. Storing style attributes in one file provides several advantages as faster loading times, the source code takes a radical diet, if all the attributes do not appear on the pages itself.