i use windows xp sevice pack 1.

i use the css validator to check whether my code is css compliant.
in my stylesheet i use the opacity codes:

filter:alpha(opacity=75);
-moz-opacity:0.75;
opacity:0.75;
-khtml-opacity:0.75;
padding-top: 10px;

when i test it in IE6 and Firefox 1.5.06 it works pretty well. i use it to make my text areas semitransparent so that the background image shows through it.

when i check it with cssvalidator it says:
<--------------QUOTE-------------->
To work as intended, your CSS style sheet needs a correct document parse tree. This means you should use valid HTML.
Errors
URI : http://www.cyaneyed.frih.net/homestyle.css

    * Line: 11 Context : body

      Parse Error - opacity=75)
    * Line: 12 Context : body

      Parse Error - -moz-opacity:0.75;
    * Line: 18

      Parse Error - :0.75; -khtml-opacity:0.75; padding-top: 10px; } 
<------------------END QUOTE---------------------->

but if the browsers interpret it correctly then why is the css validator saying that its not valid css.