Alright, well, this does require Firefox...but I have good news. I found a way to block the advertisements AND all that blank white space at the top. Follow these instructions carefully.
Step 1: If you don't have Firefox already, get it
here. Configure it, etc.
Step 2: Download these 2 extensions in Firefox after installing the browser -
AdBlock 0.5.2
ChromEdit
Step 3: Restart Firefox, then click on Tools - Adblock - Preferences
Step 4: Add 3 new filters:
http://images.neopets.com/buttons/*
http://images.neopets.com/728ads/*
http://images.neopets.com/ads/*
Click Add button to save them. Then click done.
Step 5: Go to Tools - Edit User Files, then click on the userContent.css tab.
Step 6: Scroll all the way to the end, then enter a new line:
#ban { display: none !important; }
Click the Save button.
Step 7: Restart Firefox and enjoy an ad-free NeoPets experience.