The Transparency feature is a boon when examining a page for small differences in the absolute position and size of items on Twin-view pages. EEview displays second window at 50% intensity with the white areas transparent and both windows are positioned at the top-left of the screen.

Click the Transparency button.
Clicking again switches back to Twin view, with the windows side-by-side.
oTo show the windows full-screen whenever EEview is in Transparency mode, select Maximize when aligned from the Information Options sub-menu.