var day_of_week = new Array('Lu','Ma','Mi','Ju','Vi','Sá','Do');
var month_of_year = new Array('Enero','Febrero','Marzo','Abril','Mayo','Junio','Julio','Agosto','Septiembre','Octubre','Noviembre','Diciembre');

var Calendar = new Date();
var month = Calendar.getMonth();
var year = Calendar.getFullYear();
var today = Calendar.getDate();
var weekday = Calendar.getDay()-1;
if (weekday == -1) weekday = 6;
Calendar.setDate(1);

var Primer = new Date();
Primer.setDate(1);
var espais = Primer.getDay()-1;
if (espais == -1) espais = 6;

var DAYS_OF_WEEK = 7;
var DAYS_OF_MONTH = new Date(year, month+1, 0).getDate();
var cal;

var TR_start = '<tr>';

var TR_end = '</tr>';

var highlight_start = '<td width="30"><table><tr><td width="20" style="font-size:10px; color:#FF0000; font-weight:bold;">';

var highlight_end   = '</td></tr></table>';

var TD_start = '<td width="30" style="font-size:10px;">';

var TD_end = '</td>';

cal =  '<table><tr><td style="font-size:10px;">';
cal += '<table width="185" style="border-style:solid; border-color:#000000; border-width:1px 1px 1px 1px; text-align:center;" cellspacing="0" cellpadding="2">' + TR_start;

cal += '<td colspan="' + DAYS_OF_WEEK + '" bgcolor="#EFEFEF" style="font-size:12px;">';

cal += '&nbsp;<span style="font-weight:bold;">' + month_of_year[month] +'&nbsp;'+ year + '</span>' + TD_end + TR_end;

cal += TR_start ;

for (index=0; index < DAYS_OF_WEEK; index++) {
if (index == weekday) cal += TD_start + '<span style="color:#0000FF; font-weight:600;">' + day_of_week[index] + '</span>' + TD_end;
else cal += TD_start + day_of_week[index] + TD_end;
}

cal += TR_end;

var hiha_espai = 0;
var tenim_espai = '';
for (index=0; index < DAYS_OF_WEEK; index++) {
if (index < espais) {
tenim_espai += TD_start + '&nbsp;&nbsp;' + TD_end;
hiha_espai = 1;
}
}

var week_day;
var day;
for (index=0; index < DAYS_OF_MONTH; index++) {

day = Calendar.getDate();
week_day = Calendar.getDay()-1;
if (week_day == -1) week_day = 6;

if (week_day == 0 || index == 0) cal += TR_start;

if (hiha_espai == 1 && index == 0) cal += tenim_espai;

if (today == day) cal += highlight_start + day + highlight_end + TD_end;
else cal += TD_start + day + TD_end;

if (week_day + 1 == DAYS_OF_WEEK) cal += TR_end;
Calendar.setDate(Calendar.getDate()+1);

}
cal += '</table></td></tr></table>';

document.write(cal);