function check_form(f) {
if(!check_email(f.email.value)){
alert("The e-mail address you entered does not appear to be valid. Please try again.");
f.email.focus(); 
if(document.all || document.getElementByID){
f.email.style.background = "yellow";
}
return false;
}
else {
if(document.all || document.getElementByID){
f.email.style.background = "none";
}
}
}

function check_email(e) {
ok = "1234567890qwertyuiop[]asdfghjklzxcvbnm.@-_QWERTYUIOPASDFGHJKLZXCVBNM";
for(i=0; i < e.length ;i++){
if(ok.indexOf(e.charAt(i))<0){ 
return (false);
}	
} 
if (document.images) {
re = /(@.*@)|(\.\.)|(^\.)|(^@)|(@$)|(\.$)|(@\.)/;
re_two = /^.+\@(\[?)[a-zA-Z0-9\-\.]+\.([a-zA-Z]{2,4}|[0-9]{1,3})(\]?)$/;
if (!e.match(re) && e.match(re_two)) {
return (-1);		
} 
}
}