function largoClave()
{
//detecta broser, version y plataforma

	var useragent = navigator.userAgent;
	var bName = (useragent.indexOf('Opera') > -1) ? 'Opera' : navigator.appName;
	var pos = useragent.indexOf('MSIE');
	
	if (pos > -1) {
	bVer = useragent.substring(pos + 5);
	var pos = bVer.indexOf(';');
	var bVer = bVer.substring(0,pos);
	}
	var pos = useragent.indexOf('Opera');
	if (pos > -1)	{
	bVer = useragent.substring(pos + 6);
	var pos = bVer.indexOf(' ');
	var bVer = bVer.substring(0, pos);
	}
	if (bName == "Netscape") {
	var bVer = useragent.substring(8);
	var pos = bVer.indexOf(' ');
	var bVer = bVer.substring(0, pos);
	}
	if (bName == "Netscape" && parseInt(navigator.appVersion) >= 5) {
	var pos = useragent.lastIndexOf('/');
	var bVer = useragent.substring(pos + 1);
	}
	
	var passsz;
	
	if (navigator.platform.indexOf('Win')==0)
	{
		//pc netscape
		if (bName=="Netscape" && parseInt(bVer) < 5)	
			{passsz=3;}		
		else if (bName=="Netscape" && parseInt(bVer) >=5 && parseInt(bVer) < 6)
			{passsz=1;}
		else if ((bName=="Netscape" && parseInt(bVer) >= 6))
			{passsz=1;}
	
		//pc explorer
		if (bName=="Microsoft Internet Explorer" && parseInt(bVer) < 5)	
    		{passsz=4;}
		else if (bName=="Microsoft Internet Explorer" && parseInt(bVer) >= 5 && parseInt(bVer) <= 6)
    		{passsz=3;}	
	}
	else
	{
		//mac netscape
		if (bName=="Netscape" && parseInt(bVer) < 5)	
			{passsz=8;}		
		else if (bName=="Netscape" && parseInt(bVer) >=5 && parseInt(bVer) < 6)
			{passsz=6;}
		else if ((bName=="Netscape" && parseInt(bVer) >= 6))
			{passsz=6;}
	
		//mac explorer
		if (bName=="Microsoft Internet Explorer" && parseInt(bVer) < 5)	
    		{passsz=6;}
		else if (bName=="Microsoft Internet Explorer" && parseInt(bVer) >= 5 && parseInt(bVer) <= 6)
    		{passsz=5;}
			
	}
	return (passsz);
}