We are using ExtJS 4.0.0 in our application. All the background images of extjs does not show up when the application is accessed in High Contrast Mode. For ex: the ext-all.css has trigger.gif as background image and it does not show up in High contrast mode :

.x-form-trigger {
background-image: url("../../resources/themes/images/default/form/trigger.gif");
background-position: 0 0;
border-bottom: 1px solid #B5B8C8;
cursor: pointer;
float: left;
height: 21px;
width: 17px;


Kindly let me know how can we make these background images visible in High Contrast mode also?