Parse Error with Opacity

Question

I got this http://pastebin.com/thfyTJ0K

.opacity0 {
display:block !important;

-moz-transition:all 500ms ease 0s;
-o-transition:all 500ms ease 0s;
-webkit-transition:all 500ms ease 0s;
transition:all 500ms ease 0s;

-moz-opacity: 0;
-khtml-opacity: 0;
opacity: 0;
-ms-filter: ~"progid:DXImageTransform.Microsoft.Alpha(Opacity=0)";
filter: ~progid:DXImageTransform.Microsoft.Alpha(opacity=0);
filter:alpha(opacity=0);
}

.opacity50 {
display:block !important;

-moz-transition:all 500ms ease 0s;
-o-transition:all 500ms ease 0s;
-webkit-transition:all 500ms ease 0s;
transition:all 500ms ease 0s;

-moz-opacity: 0.5;
-khtml-opacity: 0.5;
opacity: 0.5;
-ms-filter: ~"progid:DXImageTransform.Microsoft.Alpha(Opacity=0.5)";
filter: ~progid:DXImageTransform.Microsoft.Alpha(opacity=0.5);
filter:alpha(opacity=0.5);
}

.opacity1 {
display:block !important;

-moz-transition:all 500ms ease 0s;
-o-transition:all 500ms ease 0s;
-webkit-transition:all 500ms ease 0s;
transition:all 500ms ease 0s;

-moz-opacity: 1;
-khtml-opacity: 1;
opacity: 1;
-ms-filter:~"progid:DXImageTransform.Microsoft.Alpha(Opacity=100)";
filter: ~progid:DXImageTransform.Microsoft.Alpha(opacity=100);
filter:alpha(opacity=1);    
}

When i do grunt (i use Recess to compile Less) i got a Parser Error with the lines containing progid:DXImageTransform.Microsoft.Alpha. I tried putting ~ these lines but it didn't work

Answer 1

.opacity50 {
    -ms-filter: ~"progid:DXImageTransform.Microsoft.Alpha(opacity=50)";
     filter: ~"progid:DXImageTransform.Microsoft.Alpha(opacity=50)";
}

Also: use (opacity=50) instead of (opacity=.5)