Event.observe(window, "load", function(){
    $$(".datatable").each(function(thisDT){
        firstrow = true;
        even = false;
        Element.getElementsBySelector(thisDT, "tr").each(function(thisTR){
            if(firstrow)
            {
                thisTR.className = "first";
                firstrow = false;
            }
            else if (even)
                thisTR.className = "even";
            else
                thisTR.className = "odd";
                
            even = !even;
            
            firstcolumn = true;
            evenCol = false;
            Element.getElementsBySelector(thisTR, "td").each(function(thisTD){
                if(firstcolumn)
                {
                    thisTD.className = "first";
                    firstcolumn = false;
                }
                else if (evenCol)
                    thisTD.className = "even";
                else
                    thisTD.className = "odd";
                    
                evenCol = !evenCol;
            });
        });
    });
});