Verifying that all form fields are filled in
Couple of suggestions from my end.

1 > There is a better way to check null or empty in javascript,this can be done more efficiently with this

 if (document.getElementById('fname').value)
 {
   //value exists.
 }


Above condition evaluates to true if value is not equal to any of the following:


null 
undefined 
NaN 
empty string ("") 
0 
false


2 > Try to use switch case instead of so many if else.It will make your code more elegant and readable.

3 > Take care of indentation currently it's not very good.

4 > Instead of writing ewForm.checkbox[0].checked == false you can use

if(!ewForm.checkbox[0].checked) 
{
//not checked
}