function checkRate(input)
{
 var re = /^[0-9]+.?[0-9]*$/; //判断字符串是否为数字,//若判断正整数，则后边是：/^[1-9]+[0-9]*]*$/
 if (!re.test(input.rate.value))
 {
 alert("请输入数字(例:0.02)");
 input.rate.focus();
 return false;
 }
}

function BASEisNotNum(theNum)
{
if (BASEtrim(theNum)=="")
return true;
for(var i=0;i<theNum.length;i++){
oneNum=theNum.substring(i,i+1);
if (oneNum<"0" || oneNum>"9")
return true;
}
return false;
}

function BASEisNotInt(theInt)
{
theInt=BASEtrim(theInt);
if ((theInt.length>1 && theInt.substring(0,1)=="0") || BASEisNotNum(theInt)){
return true;
}
return false;
}

function ismonth(str) 
{
for(ilen=0;ilen<str.length;ilen++)
{
if(str.charAt(ilen) < '0' || str.charAt(ilen) > '9' )
{
if((str.charAt(ilen)!='-'))
return false;
} 
}
return true;
}

function BASEisNotFloat(theFloat)
{
len=theFloat.length;
dotNum=0;
if (len==0)
return true;
for(var i=0;i<len;i++){
oneNum=theFloat.substring(i,i+1);
if (oneNum==".")
dotNum++;
if ( ((oneNum<"0" || oneNum>"9") && oneNum!=".") || dotNum>1)
return true;
}
if (len>1 && theFloat.substring(0,1)=="0"){
if (theFloat.substring(1,2)!=".")
return true;
}
return false;

<script>
if(isNaN(document.login.imgcode.value)){
alert('验证码不是数字！')
document.login.imgcode.focus();
return false;
}
</script>