Here is a list of predefined validators. You cannot use these names for your custom validators. <table width="500"> <tr> <td> <b>name</b> </td> <td> <b>arguments</b> </td> <td> <b>task</b> </td> </tr> <tr> <td> email </td> <td> </td> <td> Checks if value is valid email. </td> </tr> <tr> <td> notblank </td> <td> </td> <td> Checks if value is not blank. </td> </tr> <tr> <td> notnull </td> <td> </td> <td> Checks if value is not null. </td> </tr> <tr> <td> country </td> <td> </td> <td> Checks if value is valid country code. </td> </tr> <tr> <td> ip </td> <td> </td> <td> Checks if value is valid internet protocol address. </td> </tr> <tr> <td> htmlcolor </td> <td> </td> <td> Checks if value is valid html color. </td> </tr> <tr> <td> nospace </td> <td> </td> <td> Checks if value has no space chars. </td> </tr> <tr> <td> range </td> <td> [min, max] </td> <td> Checks if value is in range specified by arguments. </td> </tr> <tr> <td> unique </td> <td> </td> <td> Checks if value is unique in its database table. </td> </tr> <tr> <td> regexp </td> <td> [expression] </td> <td> Checks if value matches a given regexp. </td> </tr> </table>