function get_randomCssNum()
{
    var ranCssNum= Math.floor(Math.random()*10);
	//var ranCssNum= Math.floor(Math.random()*Number of CSS you Have);
    return ranCssNum;
}

function getaCss()
{
   var whichCss=get_randomCssNum();

    var cssName=new Array(11)
     // var cssName=new Array(Number of CSS you Have)
     cssName[0]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style.css'>";
     cssName[1]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style1.css'>";
     cssName[2]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style2.css'>";   
     cssName[3]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style3.css'>";   
     cssName[4]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style4.css'>";   
     cssName[5]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style5.css'>";   
     cssName[6]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style6.css'>";   
     cssName[7]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style7.css'>";   
     cssName[8]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style8.css'>";   
     cssName[9]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style9.css'>";   
     cssName[10]="<link rel='stylesheet' type='text/css' href='http://www.arrivanoicorti.it/press/wp-content/themes/arrivanoicortiMOD/style5.css'>";   
     //I am using 11 CSS files in this example. you can add or remove ;)
     //for Add more CSS just add line like this 
     //cssName[Next Number]="<link rel='stylesheet' type='text/css' href='CSS FILE URL'>";
  	return cssName[whichCss]
  }
  document.write(getaCss());