Right now, there is a price reduction on Duet Browser for the iPad. The app let’s you view 2 browser windows simultaneously in either landscape or portrait mode.
Additionally, there is tabbed browsing and bookmarking available.
You can even drag the divider bar left/right or up/down to expand the size of one of the windows. In landscape mode you can apportion approximately 3/4 of an open window to the page you want to see by dragging the divider bar.
In portrait mode, you can almost eliminate one of the browser panes by dragging the divider bar.
For free, get it while you can.