Paginate.js - Instapaper-style pagination in Mobile Safari (WebKit)

Hey HN! Long-time lurker, first-time submitter.

A couple of nights ago, I was reading a long piece of text on my iPhone and thought how nice it would be to have Instapaper's pagination in Mobile Safari. So I made it (no App Store approval required!).

Once you've added the bookmark (it's a tad convoluted on the iPhone), you can open it on any page to add transparent tap zones. Tap the bottom or right side to scroll down one viewport height; tap the top or left side to scroll up one viewport height (the layout is the same as Instapaper). To temporarily disable pagination so you can interact with the page, tap the middle of the screen; tap the transparent overlay at the bottom to re-enable. Open the bookmarklet again to completely disable it.

I've only personally tested this on my iPhone 3G and the iPhone simulator. If you've got an iPad, Android phone, Palm Pre, or some other device with a credible WebKit browser, I'd love to know if it works fine (it probably should). If you have a fix to make it work on your device without breaking iPhone OS (iOS?) support, send it my way.

It also works in Safari and Chrome, but not in Firefox, Opera, and almost assuredly IE. I think it has something to do with the size of the bookmarklet--if someone can figure out a fix I'd love to accept it.

Feedback on the code would also be appreciated.

Thanks!