显示错误：magento中的有效电子邮件地址

I am using magento 1.8. I am new to magento, so on the checkout page, when I enter the email address, it shows a popup with " enter valid email address".

Again when I enter the email id and password in already registered column, it works.

What is the problem and where I should find the email validation file in magento ?

And how to validate the email id?

I am using this code

  <?php if(!$this->isCustomerLoggedIn()): ?>
                <div class="field">
                    <label for="billing:email" class="required"><em>*</em><?php echo $this-        >__('Email Address') ?></label>
                    <div class="input-box">
                        <input type="text" name="billing[email]" id="billing:email" value="<?php       echo $this->htmlEscape($this->getAddress()->getEmail()) ?>" title="<?php echo $this->__('Email    Address') ?>" class="string input-block-level input-text validate-email required-entry billing-email" />
                    </div>
                </div>
    <?php endif; ?>

validation of email id:

    "validate-emails": [
        function(value) {
            if ($.mage.isEmpty(value)) {
                return true;
            }
            var valid_regexp = /^[a-z0-9\._-]{1,30}@([a-z0-9_-]{1,30}\.){1,5}[a-z]{2,4}$/i,
                emails = value.split(/[\s
\,]+/g);
            for (var i = 0; i < emails.length; i++) {
                if (!valid_regexp.test(emails[i].strip())) {
                    return false;
                }
            }

You are blaming the wrong piece of code for the validation of email: the alert that pops up is from the code:

<script>
  jQuery(document).ready(function(){
    jQuery("#onepage-guest-register-button" ).click(function(){
       var mailid=jQuery('#guest-email').attr('value');
       var emailReg = /^([\w-\.]+@([\w-]+\.)+[\w-]{2,4})?$/;
       if( !emailReg.test(mailid) ){
          alert("please Enter valid Email Address")
          return false;
       }else if (jQuery('#guest-email').attr('value')==''){
          alert("please enter valid Email Address ");
          return false;
       }else{
          var mailid=jQuery('#guest-email').attr('value');
          jQuery('.bill-mail').val(mailid);
          checkout.setMethod();
       }  
    })
  })
</script>

While your generated input is:

<input type="text" class="input-text required-entry validate-email" id="guest-email" name="guest[username]" value="">

I debugged and it seems that the problem is with the else-if statement:

  else if(jQuery('#guest-email').attr('value')=='')

Try with:

 else if(jQuery('#guest-email').val()=='')