.gray{
    filter: gray; /* IE6-9 */
    -webkit-filter: grayscale(1); /* Google Chrome, Safari 6+ & Opera 15+ */
    filter: grayscale(1); /* Microsoft Edge and Firefox 35+ */ 
 }

body.gray_mode {
    background-image: url(../images/bg_gray.jpg);
    background-repeat: repeat-y repeat-x;
}

/*********************************** End Gray Mode **************************************/