//Valida fecha dd/MM/yyyy
function validaFecha( strValue ) {
  var objRegExp = /^\d{2}\/\d{2}\/\d{4}$/
  if(!objRegExp.test(strValue))
    return false;
  else {
    var arrayDate = strValue.split('/');
    var arrayLookup = { '01' : 31,'03' : 31, '04' : 30,'05' : 31,'06' : 30,'07' : 31,'08' : 31,'09' : 30,'10' : 31,'11' : 30,'12' : 31}
    var intDay = parseInt(arrayDate[0],10);
    if(arrayLookup[arrayDate[1]] != null) {
      if(intDay <= arrayLookup[arrayDate[1]] && intDay != 0)
        return true;
    }
    var intMonth = parseInt(arrayDate[1],10);
    if (intMonth == 2) { 
       var intYear = parseInt(arrayDate[2],10);
		if( ((intYear % 4 == 0 && intDay <= 29) || (intYear % 4 != 0 && intDay <=28)) && intDay !=0)
          return true;
       }
  }
  return false;
}
function colocarFondo(){
var myWidth = 0, myHeight = 0;
  if( typeof( window.innerWidth ) == 'number' ) {
    //Non-IE
    myWidth = window.innerWidth;
    myHeight = window.innerHeight;
  } else if( document.documentElement && ( document.documentElement.clientWidth || document.documentElement.clientHeight ) ) {
    //IE 6+ in 'standards compliant mode'
    myWidth = document.documentElement.clientWidth;
    myHeight = document.documentElement.clientHeight;
  } else if( document.body && ( document.body.clientWidth || document.body.clientHeight ) ) {
    //IE 4 compatible
    myWidth = document.body.clientWidth;
    myHeight = document.body.clientHeight;
  }
  
  var fondo = document.getElementById('miFondo');
  fondo.style.backgroundImage = "url('fondo.aspx?iW="+ myWidth +"&iH="+ myHeight +"')" 
}