@media(max-width:1024px)and(orientation:landscape){/* tablet and smaller */
body:after{
position:absolute;
z-index:9999;
width:100%;
top:0;
bottom:0;
content:"";
background:#212121url(http://i.stack.imgur.com/sValK.png)00no-repeat;/* replace with an image that tells the visitor to rotate the device to landscape mode */
background-size:100%auto;
opacity:0.95;
}
body:after{
position:absolute;
z-index:9999;
width:100%;
top:0;
bottom:0;
content:"";
background:#212121url(http://i.stack.imgur.com/sValK.png)00no-repeat;/* replace with an image that tells the visitor to rotate the device to landscape mode */