.left_bg {display: block; float: left; background: red; height: 600px; width: 50%; position: absolute; left: 0; z-index: 1}
.right_bg {display: block; float: right; background: green; height: 600px; width: 50%; position: absolute; right: 0; z-index: 1}
.center_bg {position: absolute; z-index: 4; background: purple; height: 600px; width: 100%; margin: 0 auto 0 auto;}

/* 1 */
.rnd_bg_1 { background: #FFF; }
.rnd_bg_1 .left_bg { background: transparent url(images/headers/1_lr.jpg) repeat-x; }
.rnd_bg_1 .right_bg { background: transparent url(images/headers/1_lr.jpg) repeat-x; }
.rnd_bg_1 .center_bg { background: transparent url(images/headers/1.jpg) no-repeat center top; }

/* 2 */
.rnd_bg_2 { background: #FFF; }
.rnd_bg_2 .left_bg { background: transparent url(images/headers/2_lr.gif) repeat-x; }
.rnd_bg_2 .right_bg { background: transparent url(images/headers/2_lr.gif) repeat-x; }
.rnd_bg_2 .center_bg { background: transparent url(images/headers/2.gif) no-repeat center top; }

/* 3 */
.rnd_bg_3 { background: #000; }
.rnd_bg_3 .left_bg { background: transparent url(images/headers/3_lr.jpg) repeat-x; }
.rnd_bg_3 .right_bg { background: transparent url(images/headers/3_lr.jpg) repeat-x; }
.rnd_bg_3 .center_bg { background: transparent url(images/headers/3.jpg) no-repeat center top; }

/* 4 */
.rnd_bg_4 { background: #000; }
.rnd_bg_4 .left_bg { background: transparent url(images/headers/4_lr.jpg) repeat-x; }
.rnd_bg_4 .right_bg { background: transparent url(images/headers/4_lr.jpg) repeat-x; }
.rnd_bg_4 .center_bg { background: transparent url(images/headers/4.jpg) no-repeat center top; }

/* 5 */
.rnd_bg_5 { background: #000; }
.rnd_bg_5 .left_bg { background: transparent; }
.rnd_bg_5 .right_bg { background: transparent; }
.rnd_bg_5 .center_bg { background: transparent url(images/headers/5.jpg) no-repeat center top; }

/* 6 */
.rnd_bg_6 { background: #000; }
.rnd_bg_6 .left_bg { background: transparent url(images/headers/6_lr.jpg) repeat-x; }
.rnd_bg_6 .right_bg { background: transparent url(images/headers/6_lr.jpg) repeat-x; }
.rnd_bg_6 .center_bg { background: transparent url(images/headers/6.jpg) no-repeat center top; }

/* 7 */
.rnd_bg_7 { background: #FFF url(images/headers/7_body.gif) repeat-y center top; }
.rnd_bg_7 .left_bg { background: transparent; }
.rnd_bg_7 .right_bg { background: transparent; }
.rnd_bg_7 .center_bg { background: transparent url(images/headers/7.gif) no-repeat center top; }