add more refs to browser-related bugs in Less comments

less/carousel.less

@@ -196,6 +196,7 @@
     // Internet Explorer 8-9 does not support clicks on elements without a set
     // `background-color`. We cannot use `filter` since that's not viewed as a
     // background color by the browser. Thus, a hack is needed.
+    // See https://developer.mozilla.org/en-US/docs/Web/Events/click#Internet_Explorer
     //
     // For IE8, we set solid black as it doesn't support `rgba()`. For IE9, we
     // set alpha transparency for the best results possible.

less/close.less

@@ -23,6 +23,7 @@
   // Additional properties for button version
   // iOS requires the button element instead of an anchor tag.
   // If you want the anchor version, it requires `href="#"`.
+  // See https://developer.mozilla.org/en-US/docs/Web/Events/click#Safari_Mobile
   button& {
     padding: 0;
     cursor: pointer;

less/forms.less

@@ -143,7 +143,7 @@ output {
   fieldset[disabled] & {
     cursor: @cursor-disabled;
     background-color: @input-bg-disabled;
-    opacity: 1; // iOS fix for unreadable disabled content
+    opacity: 1; // iOS fix for unreadable disabled content; see https://github.com/twbs/bootstrap/issues/11655
   }
 
   // Reset height for `textarea`s

less/theme.less

@@ -36,7 +36,7 @@
 // Mixin for generating new styles
 .btn-styles(@btn-color: #555) {
   #gradient > .vertical(@start-color: @btn-color; @end-color: darken(@btn-color, 12%));
-  .reset-filter(); // Disable gradients for IE9 because filter bleeds through rounded corners
+  .reset-filter(); // Disable gradients for IE9 because filter bleeds through rounded corners; see https://github.com/twbs/bootstrap/issues/10620
   background-repeat: repeat-x;
   border-color: darken(@btn-color, 14%);
 
@@ -130,7 +130,7 @@
 // Inverted navbar
 .navbar-inverse {
   #gradient > .vertical(@start-color: lighten(@navbar-inverse-bg, 10%); @end-color: @navbar-inverse-bg);
-  .reset-filter(); // Remove gradient in IE<10 to fix bug where dropdowns don't get triggered
+  .reset-filter(); // Remove gradient in IE<10 to fix bug where dropdowns don't get triggered; see https://github.com/twbs/bootstrap/issues/10257
 
   .navbar-nav > .open > a,
   .navbar-nav > .active > a {