E-Mail format checking script

if (document.formname.fieldname.value.length >0) {
i=document.formname.fieldname.value.indexOf("@")
j=document.formname.fieldname.value.indexOf(".",i)
k=document.formname.fieldname.value.indexOf(",")
kk=document.formname.fieldname.value.indexOf(" ")
jj=document.formname.fieldname.value.lastIndexOf(".")+1
len=document.formname.fieldname.value.length

if ((i>0) && (j>(1+1)) && (k==-1) && (kk==-1) && (len-jj >=2) && (len-jj<=3)) {
}
else {
alert("Please enter an exact email address.\n" +
document.formname.fieldname.value + " is invalid.");
return false;
}

}