var dom = (document.getElementById) ? true : false;
  var ff1 = ((navigator.userAgent.indexOf("Firefox")>-1) && dom) ? true: false;
  var ns5 = ((navigator.userAgent.indexOf("Gecko")>-1) && dom) ? true: false;
  var ie5 = ((navigator.userAgent.indexOf("MSIE")>-1) && dom) ? true : false;
  var ns4 = (document.layers && !dom) ? true : false;
  var ie4 = (document.all && !dom) ? true : false;
  var nodyn = (!ns5 && !ns4 && !ie4 && !ie5) ? true : false;



//if checkbox of any weatherOpt is checked -> the others will be unchecked
function useWeatherOption(weatherOpt){

	

	if(weatherOpt == 'td' || weatherOpt == 'td1' || weatherOpt == 'td2'){
	
			if(weatherOpt != 'td' && document.getElementById('td').checked == true && document.getElementById(weatherOpt).checked == true)
			{
			 	document.getElementById('td').checked = false;
				document.getElementById(weatherOpt).checked = true;
			}
			if(weatherOpt != 'td1' && document.getElementById('td1').checked == true && document.getElementById(weatherOpt).checked == true)
			{
				document.getElementById('td1').checked = false;
				document.getElementById(weatherOpt).checked = true;
			}
			if(weatherOpt != 'td2' && document.getElementById('td2').checked == true && document.getElementById(weatherOpt).checked == true)
			{
				document.getElementById('td2').checked = false;
				document.getElementById(weatherOpt).checked = true;
			}
	}else{
	
			if(weatherOpt != 'mor' && document.getElementById('mor').checked == true && document.getElementById(weatherOpt).checked == true)
			{	
				document.getElementById('mor').checked = false;
				document.getElementById(weatherOpt).checked = true;
			}
			if(weatherOpt != 'aft' && document.getElementById('aft').checked == true && document.getElementById(weatherOpt).checked == true)
			{
				document.getElementById('aft').checked = false;
				document.getElementById(weatherOpt).checked = true;
			}
			if(weatherOpt != 'eve' && document.getElementById('eve').checked == true && document.getElementById(weatherOpt).checked == true)
			{
				document.getElementById('eve').checked = false;
				document.getElementById(weatherOpt).checked = true;
			}
			if(weatherOpt != 'nig' && document.getElementById('nig').checked == true && document.getElementById(weatherOpt).checked == true)
			{
				document.getElementById('nig').checked = false;
				document.getElementById(weatherOpt).checked = true;
			}
	}

}