Prasanna Shrestha

By Default Magento give number of validation classes.you just need to use the class name.Its easy find the html tag where their is mobile number html and add a class attribute to that input type and under the class add the following classes  "validate-length maximum-length-10 minimum-length-10 validate-digits" validate-length maximum-length-10 minimum-length-10 validate-digits Reference: http://inchoo.net/magento/out-of-the-box-form-validation-in-magento/