In a previous article, I've put form validation the first in the list of "what every contact form should have". Today I am gonna talk about this a little more, because I feel many people do not understand the real value of form validation.
Form validation is obtained using special created scripts, that take the input values and compare them with the expected input format (an email address, a numeric value, an alphanumeric string, a valid date, a valid time etc). There are 2 categories of form validation scripts: client-side scripts (usually JavaScript) and server-side (PHP, ASP etc). They both have advantages and disadvantages. JavaScript form validation is very powerful, but it becomes useless if the visitor's browser has JavaScript disabled. Server-side form validation usually needs the page to be reloaded for the validation to take place, but it can be considered more reliable.
There are many form validation options, each having its own usage. For example, if you run a hotel, and you want to let your customers reserve rooms using your website, you probably have a contact form that asks for a name, a valid email, a valid phone number, a valid check-in date, a valid check-out date, and maybe other fields. If your form does not have form validation, and your customers enters, by mistake, an invalid email and an invalid phone number, you won't be able to contact the customer to confirm the reservation, so you'll probably lose money! This is why you must use form validation, and make sure your visitors enter the expected data in your form's fields.
All the major online form generators offer form validation. I recommend you 123ContactForm form validation, especially if you need advanced form validation, ie: alpha (only letters), alphanumeric (only letters and numbers), alphaspace (letters and spaces), alphanumericspace (letters, numbers, spaces), numeric, numericplus (numbers plus .+-).
