Clickable link:
http://sharebookbox.com/Nice widget!
For the UI, consider making the steps the user should take to create the widget more clear. You could have "Step 1", "Step 2", "Step N" spelled out, for instance.
Also, I wasn't sure why I needed to enter in a password to get the widget code. To me, a password means a user account is involved somehow, though that's clearly not the case here. Perhaps the word "password" could be replaced. Or an explanation can be offered.
I applaud the effort to learn JavaScript. It's a good language to know. Although many embeddable widgets also use document.write like you do, this has some performance implications. Here's an article with more info about that:
http://www.schillmania.com/content/entries/2009/defer-script...
Google Analytics recently implemented a performance improvement that's related to this issue:
http://searchengineland.com/google-analytics-releases-new-fa...
For further JavaScript geekery, you can consider something similar.
Lastly, you can try that pop-up layer from KISSinsights (http://www.kissinsights.com/) that's been popping up (no pun intended) on various sites lately. It's basically a survey with which you can ask your audience whatever questions you'd like. Perhaps you can get some more feedback that way. And Andrew Warner from Mixergy reported that it gave more feedback than GetSatisfaction.com:
http://mixergy.com/kissinsights-so-far/
I hope this helps. Good luck!