Error meassage

I am using Win98 second Edition, and Explore 5.5. when I was on internet it occur a meassag:

An error has occurred in the script on this page
Line : 4
Char: 1
error: ” document. forms.1. serid” is null or not an object.
Url: …….
Do you want to continue runing scripts on this pae.

What is wrong?? could be my Explore or win98???
Any help will help!

Thanks very much.

Tina