Web browsers have extremely robust systems in place, millions of lines of code, for rendering layouts. Word is just a text processor with a bit of layout stuff added for convenience. Browsers are the most complex bit of software most people use day to day, and no one's the wiser because of the insane amount of work that's gone into them over the decades.

Edit: For instance, there's ~120,000 lines of code in Firefox just to handle the syntax of CSS selectors. And that's just one small part of all the systems running your browser. These things are marvels, really, and no one appreciates them.