function is_empty(theField)
{
	if (theField.value ==""|| theField.value==null|| theField.value==0) {
	alert('Please enter your ' + theField.name); 
    theForm.focus();
	return false;
	}
	else return true;
}

function validateForm(theForm) {

var flag = !is_empty(theForm.name);

if(flag) flag = !is_empty(theForm.name);
if(flag) flag =!is_empty(theForm.age);
if(flag) flag = !is_empty(theForm.sex);
if(flag) flag = !is_empty(theForm.city);
if(flag) flag = !is_empty(theForm.email);

return flag;

}