You can try using this code:
#container { display:block; }
@media only screen and (orientation:portrait){
#container {
height: 100vw;
-webkit-transform: rotate(90deg);
-moz-transform: rotate(90deg);
-o-transform: rotate(90deg);
-ms-transform: rotate(90deg);
transform: rotate(90deg);
}
}
@media only screen and (orientation:landscape){
#container {
-webkit-transform: rotate(0deg);
-moz-transform: rotate(0deg);
-o-transform: rotate(0deg);
-ms-transform: rotate(0deg);
transform: rotate(0deg);
}
You should also add this to the body tag:
<BODY id="container">
I found this solution here. Same blog also offers additional suggestion but I didn't tried it as the above one worked well