Even with today’s super-fast computers, it still takes extra time to load PDF files, Quicktime movies, and other browser plugins — especially if the files are large. Considering how quickly users will abandon a website or application that responds slowly, it’s important to let people know what to expect before they click your links. As a rule of thumb, if you’re linking to something that isn’t a regular webpage, requires a plugin, or opens in another program entirely, make sure to give the user fair warning of the file type and size. Something like “Download the user’s guide (PDF, 5 MB)” or “Watch the demo video (Quicktime, 20 MB)” can go a long way towards managing expectations and keeping your users happy.