These individual technologies (DOM/html parser, js runtime, layout etc.) really aren't so bad. It's about a weekends worth of work to do one. What makes a "mod

These individual technologies (DOM/html parser, js runtime, layout etc.) really aren't so bad. It's about a weekends worth of work to do one. What makes a "modern" browser is all of these technologies together not just quirk free, but matching quirks with whatever browser is popular. Even this won't really be enough since most people also depend on a bunch of online services provided by browser vendors at this point (push, bookmark syncing, password management etc.)