JS opacity element has absolutely no effect on my DIV box in Chrome

Question

Hi I have a js script below and I am hoping that the opacity will be very minimal on my page . But it has absolutely no effect what ever the value . Can anyone suggest what I am doing wrong please ?. thanks

    dx = document.getElementById('box').style

dx.backgroundColor= '#fff' 
dx.visibility = "visible";
dx.width = 800 + "px" ;
dx.height = 40 + "px" ;
dx.top = 600 + "px" ;
dx.overflow = "hidden" ;
dx.marginLeft = "-400px";

tab = "<table width='800' border='0' cellpadding='1' > <tr> <td width='75' ></td> <td width='200'></td> <td width='75' ></td> <td ></td>  </tr>  <tr> <td align='left' valign='middle'><div align='right'>Contact</div></td> <td colspan='4' align='left' valign='middle'><input name='Pcontact' type='text' id='Pcontact' size='20' /> Number <input name='Pnumber' type='text' id='Pnumber' size='20' /> Mail <input name='Pmail' type='text' id='Pmail' size='25' /> <input name='addcontact' type='button' id='addcontact' value='Add Contact'  /></td> </tr> </table>" ;

document.getElementById('box').innerHTML = tab 

dx.opacity = 10 ;

in a css I have the following for my box

#box {
position:fixed;
width: 600px;
height: 700px;
top: 40px ; 
border: 2px solid black;
background-color:#CCC; 
left:50% ; 
margin-left:-300px;
visibility:hidden ;
overflow:scroll ; 

}

The box div is sized in my js as it has multiple uses

Answer 1

opacity has a range of 0 to 1, you are setting it to 10.

You probably mean 0.1 or perhaps 0.9.

Answer 2

Would this work for you? Or do you need all of the elements transparent?

#box {
position:fixed;
width: 600px;
height: 700px;
top: 40px ; 
border: 2px solid black;
background-color:rgba(204, 204, 204, 0.1);
left:50% ; 
margin-left:-300px;
visibility:hidden ;
overflow:scroll ; 
}

http://www.css3.info/introduction-opacity-rgba/

Answer 3

Just to be complete, you really should be doing:

var opacity = 10;
dx.opacity = (opacity/100); // standard
dx.MozOpacity = (opacity/100); // older firefox
dx.KhtmlOpacity = (opacity/100); // older safari
dx.filter = “alpha(opacity=” + opacity + “)”; // IE

Although, personally I just do:

var opacity = 10;
dx.opacity = (opacity/100); // standard
dx.filter = “alpha(opacity=” + opacity + “)”; // IE

since Firefox and Safari users typically upgrade their browsers.