var rowDisplayStyle = document.defaultView ? "table-row" : "block"; // table-row for Mozilla and Opera, block for MSIE

function hideElement(elementname)
{
    var myElement = document.getElementById(elementname);
    myElement.style.display = 'none';
}

function showElement(elementname)
{
    var myElement = document.getElementById(elementname);
    if(myElement !== null)
        myElement.style.display = rowDisplayStyle;
}

function hidePreventivi()
{
     for(i=0; i<(arguments.length); i++)
     {
        hideElement('cat_'+arguments[i]);
     }
}