ASP.NET web controls

Does text box have "lost focus" event? For example, there are two text boxes, txtAccountNumber and txtName. Once user inputs account number into txtAccountNumber and move to txtName before inputing name,  I want to fire a sub to verify this account number. ...

When I write a custom validator (by inheriting from the BaseValidator class) and add a JavaScript function for client-side validation, Firefox does not use it. All my validators work perfectly fine in Internet Explorer, and I'm not using any browser-specific JavaScript or getting any JavaScript errors, ...