/*created by JoshT@j-3media.com
*Use with a bunch of divs with IDs   SomeID1, SomeID2, SomeID3
*each of these divs needs a css class of hidden that sets display:none
*
*.show{display:block;}
*.hidden{display:none;}
*<div id="SomeID1" class="hidden"></div>
*
*/

 function rand( min, max ) {
    var argc = arguments.length;
    if (argc == 0) {
        min = 0;
        max = 2147483647;
    } else if (argc == 1) {
        throw new Error('Warning: rand() expects exactly 2 parameters, 1 given');
    }
    return Math.floor(Math.random() * (max - min + 1)) + min;
}


//change the rand function to the appropriate numbers and change DIV_ID to your div id's
var curDiv = document.getElementById("city"+rand(1,37));
curDiv.className = "show";