The HTML fields for the password and retype password inputs on the account creation dialog - Special:UserLogin/signup - are marked as required fields (required="required"). However a password is not always required for account creation. When creating an account by email using the "by Email" option a random password will be automatically generated for the new account, and the password field isn't required. Since the password fields are marked as required, browsers that enforce the "required" attribute (including Google Chrome, Opera) will not allow account creation by email without a password being supplied, while those that don't (Firefox, Internet Explorer) will. Suggested resolution is to remove the "required" attribute from the inputbox.