>Hi,
> I would like to know that, how does validation data being done, when user press save button or lost locus/valid for each controls??
>

It depends on the type of interface you write; for VFP forms, where each field is independently capable of being validated, most of my users prefer to be told up front when they've entered an incorrect or invalid value, and then have final validation performed on the record as whole on save.

This approach doesn't work easily for HTML, where the client's browser is handling the input, and sends a screenful of data back to the application all at one time; it's also difficult to program where the values of many fields on the screen interact for validation.

It's really a design issue, and one that your end-users' requirtements should dictate.