onload=function(){
    ColoraRighe();
    };

function ColoraRighe(){
var tabelle=document.getElementsByTagName("table");
for(i=0;i<tabelle.length;i++){
    if(tabelle[i].className.indexOf("righealterne")>=0){
        trs=tabelle[i].tBodies[0].rows;
        for(j=1;j<trs.length;j+=2)
            trs[j].className="alterna";
        }
    }
}