Email double verification

1. Create custom.js file - Using custom.css and custom.js

2. Add the following code inside created custom.js

   document.observe('dom:loaded', function() {
       var email = $('billing:email');
       if (!email || !email.up('li')) {
           return;
       }
   
       email.up('li').insert({
           after:
               '<li class="wide">' +
                   '<label class="required">Enter your email again please</label>' +
                   '<div class="input-box">' +
                       '<input id="billing:email_confirm" placeholder="Enter your email again please *" class="input-text required-entry validate-both-emails" type="text">' +
                   '</div>' +
               '</li>'
       });
   
       Validation.add(
           'validate-both-emails',
           'Email did not match the email above',
           function(v, input) {
               var dependentInput = $('billing:email'),
                   isEqualValues  = (input.value.toLowerCase() == dependentInput.value.toLowerCase());
   
               if (isEqualValues && dependentInput.hasClassName('validation-failed')) {
                   Validation.test(this.className, dependentInput);
               }
   
               return isEqualValues;
           }
       );
   });
   

3. Save file and disable js merge if needed.

Screenshot