Probably because you have errors in the code.
Just for starters:
Code:
document.write("Last name: " + this.lName + BR);
document.write("First name: " + this.fName + BR);
Compare that to:
Code:
function Account(type, num, lName, fName, bal) {
this.acctType = type;
this.acctNumber = num;
this.lastName = lName;
this.firstName = fName;
...
But now...
If that book is required for some class, then you need to report the instructor to the school as incompetent to teach the subject, since he chose a book that is over 10 years out of date.
If you chose it yourself, then consider using it for its highest possible purpose: fire kindling.
document.write stopped being necessary with Netscape 4 and became even less advisable with MSIE 5. 1998 and 1999 or so. It is considered obsolete, bad coding, and inappropriate for modern usage (with a few very advanced exceptions).