Our minds do not think inside of pages, files or apps. We think in concepts, we dart around fluidly at whatever level of detail suits the moment, connecting the dots, sparking aha moments. Information technology could be augmenting our collective human intellect at the speed of thought in powerful new ways, instead of automating how we used to think and work in a linear paper-based world.
Browsers should be able to support this. Instead of opening an interesting-looking link in the background, the preview appears in a sidebar, aligned with the link. Available, but not distracting from the main purpose of reading.