function applyShadow() {

    //calculates the length of the right and left horizontal shadows against
    // frame(div) height and apply them

    //Note difference between left shadow and frame(div) height is 42px
    //and difference between right shadow and div frame height is 55px
    
    var divFrameHeigh = document.getElementsByTagName("div")["frame"].offsetHeight
    var leftShadowHeight = document.getElementsByTagName("div")["left_shadow"].offsetHeight
    var rightShadowHeight = document.getElementsByTagName("div")["right_shadow"].offsetHeight


    if (leftShadowHeight < divFrameHeigh) {
        var diffLeft = divFrameHeigh - leftShadowHeight;
        var diffRight = divFrameHeigh - rightShadowHeight;
        valueLeft = 42 - diffLeft;
        valueRight = 55 - diffRight

        var newleftShadowHeight = leftShadowHeight - valueLeft;
        var newRightShadowHeight = rightShadowHeight - valueRight

        leftShadowHeight = newleftShadowHeight;
        rightShadowHeight = newRightShadowHeight;

        left_shadow.style.height = leftShadowHeight + "px";
        right_shadow.style.height = rightShadowHeight + "px";

    }
    else {

        left_shadow.style.height = (divFrameHeigh - 42) + "px";
        right_shadow.style.height = (divFrameHeigh - 55) + "px";

    }
}