I got this from an Apple Discussions question. It works:
If you want to go to the bottom of any web page in Safari you can do it using a bookmark and javascript.
Using your iPhone, go to any page and save a bookmark (this one will do). Then copy the following line on your iPhone (the usual way).
javascript:window.scrollTo%280%2C100000%29
Edit the bookmark you created. Rename it something like "Go to bottom" and then replace the url with the above (paste it in).
The next time you are viewing a page and want to go to the bottom, just select that bookmark and it will take you to the bottom of the page.