Remove some IE9 stuff from bootstrap.css

static/css/bootstrap.css

@@ -2302,7 +2302,6 @@ select[multiple].input-lg {
 .btn[disabled],
 fieldset[disabled] .btn {
   cursor: not-allowed;
-  filter: alpha(opacity=65);
   opacity: 0.65;
   box-shadow: none;
 }
@@ -2802,7 +2801,6 @@ tbody.collapse.in {
   cursor: not-allowed;
   background-color: transparent;
   background-image: none;
-  filter: progid:DXImageTransform.Microsoft.gradient(enabled = false);
 }
 .open > .dropdown-menu {
   display: block;
@@ -4262,7 +4260,6 @@ a.badge:focus {
   line-height: 1;
   color: var(--close-color);
   text-shadow: 0 1px 0 #fff;
-  filter: alpha(opacity=20);
   opacity: 0.2;
 }
 .close:hover,
@@ -4270,7 +4267,6 @@ a.badge:focus {
   color: var(--close-color);
   text-decoration: none;
   cursor: pointer;
-  filter: alpha(opacity=50);
   opacity: 0.5;
 }
 button.close {
@@ -4332,11 +4328,9 @@ button.close {
   background-color: #000;
 }
 .modal-backdrop.fade {
-  filter: alpha(opacity=0);
   opacity: 0;
 }
 .modal-backdrop.in {
-  filter: alpha(opacity=50);
   opacity: 0.5;
 }
 .modal-header {
@@ -4413,11 +4407,9 @@ button.close {
   word-wrap: normal;
   white-space: normal;
   font-size: 12px;
-  filter: alpha(opacity=0);
   opacity: 0;
 }
 .tooltip.in {
-  filter: alpha(opacity=90);
   opacity: 0.9;
 }
 .tooltip.top {

stuff/bootstrap/mixins/gradients.less

@@ -10,7 +10,6 @@
     background-image: -webkit-linear-gradient(left, @start-color @start-percent, @end-color @end-percent); // Safari 5.1-6, Chrome 10+
     background-image: -o-linear-gradient(left, @start-color @start-percent, @end-color @end-percent); // Opera 12
     background-image: linear-gradient(to right, @start-color @start-percent, @end-color @end-percent); // Standard, IE10, Firefox 16+, Opera 12.10+, Safari 7+, Chrome 26+
-    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=1)", argb(@start-color), argb(@end-color))); // IE9 and down
     background-repeat: repeat-x;
   }
 
@@ -22,7 +21,6 @@
     background-image: -webkit-linear-gradient(top, @start-color @start-percent, @end-color @end-percent);  // Safari 5.1-6, Chrome 10+
     background-image: -o-linear-gradient(top, @start-color @start-percent, @end-color @end-percent);  // Opera 12
     background-image: linear-gradient(to bottom, @start-color @start-percent, @end-color @end-percent); // Standard, IE10, Firefox 16+, Opera 12.10+, Safari 7+, Chrome 26+
-    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)", argb(@start-color), argb(@end-color))); // IE9 and down
     background-repeat: repeat-x;
   }
 
@@ -36,14 +34,12 @@
     background-image: -webkit-linear-gradient(left, @start-color, @mid-color @color-stop, @end-color);
     background-image: -o-linear-gradient(left, @start-color, @mid-color @color-stop, @end-color);
     background-image: linear-gradient(to right, @start-color, @mid-color @color-stop, @end-color);
-    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=1)", argb(@start-color), argb(@end-color))); // IE9 and down, gets no color-stop at all for proper fallback
     background-repeat: no-repeat;
   }
   .vertical-three-colors(@start-color: #00b3ee; @mid-color: #7a43b6; @color-stop: 50%; @end-color: #c3325f) {
     background-image: -webkit-linear-gradient(@start-color, @mid-color @color-stop, @end-color);
     background-image: -o-linear-gradient(@start-color, @mid-color @color-stop, @end-color);
     background-image: linear-gradient(@start-color, @mid-color @color-stop, @end-color);
-    filter: e(%("progid:DXImageTransform.Microsoft.gradient(startColorstr='%d', endColorstr='%d', GradientType=0)", argb(@start-color), argb(@end-color))); // IE9 and down, gets no color-stop at all for proper fallback
     background-repeat: no-repeat;
   }
   .radial(@inner-color: #555; @outer-color: #333) {

stuff/bootstrap/mixins/opacity.less

@@ -2,6 +2,5 @@
 
 .opacity(@opacity) {
   @opacity-ie: (@opacity * 100);  // IE8 filter
-  filter: ~"alpha(opacity=@{opacity-ie})";
   opacity: @opacity;
 }

stuff/bootstrap/mixins/reset-filter.less

@@ -4,5 +4,4 @@
 // the IE filter for IE9 and below.
 
 .reset-filter() {
-  filter: e(%("progid:DXImageTransform.Microsoft.gradient(enabled = false)"));
 }