How to change the error system messages is it possilbe to use string overrides module for system messages? What i need is to change the order of the words and add some more. For example i have a webform with some required fields. When user forget to fill a field it gets this message: "Surname field is required.". I need to change this to "The field Surname is required for this form". How can i do this?

Thank you
You can use String Overrides module. Also you can override strings through settings.php, look this post.

For example that you listed above, there is one string that contains variable !name. So "Surname field is required." is "!name field is required.", when you changing use "The field !name is required for this form" and you overrides all similar messages.