The W3C spec­i­fi­ca­tion for CSS 3 has added a new opac­i­ty prop­er­ty. Pre­vi­ous to this, Inter­net Explor­er used

filter:progid:DXImageTransform.Microsoft.Alpha(opacity=50)

and Mozil­la-based browsers used

-moz-opacity

Of course, this was not an ide­al sit­u­a­tion since it relied on cod­ing that was not based on stan­dards, some­thing the W3C has been try­ing to reduce and some­thing that was at the root of the brows­er wars of the 1990s.

The W3C intro­duced the opac­i­ty prop­er­ty in the 5 March 2001 work­ing draft ver­sion of the CSS3 spec­i­fi­ca­tion. Cur­rent­ly, the W3C spec­i­fi­ca­tion for CSS3 is only at “can­di­date rec­om­men­da­tion” sta­tus and has been for near­ly two years. This means, tech­ni­cal­ly, it is not a “stan­dard”.

That being said, Fire­fox sup­ports the opac­i­ty prop­er­ty of the CSS3 spec­i­fi­ca­tion. This is impor­tant because it proves that Fire­fox is still com­mit­ted to web stan­dards and is for­ward think­ing.

Check out these two box­es below. In Fire­fox 1.0, the top one is black and the bot­tom one is grey.

 
 

UPDATE: (31 March 2005) I just checked Safari and it sup­ports the opac­i­ty prop­er­ty of CSS3 as well. Very cool.

About Kim Siever

I am a copy­writer and copy­ed­i­tor. I blog on writ­ing tips most­ly, but I some­times throw in my thoughts about run­ning a small busi­ness.

Fol­low me on Twit­ter at @hotpepper.

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