The shocking, unprecedented, world-changing difference that the web brings is that on the web all you have to do is click a link and your computer downloads, "installs", and runs a program. No manual installation necessary, no upgrades, no installers or wizards. No delay. This process is safe -- the page is sandboxed and can't interfere with the rest of your machine. And these things can be instantly shared! All I have to do is paste a bit of text to my friends and it turns into another clickable link that's only a touch away.
Engineers frequently undervalue this feature, especially considering the things that the web give up in order to achieve it. So yes, it's a pain in the ass to get that div to align correctly but in exchange you get to run instantly and almost everywhere [1].
Relevant: http://xkcd.com/1367/
[1] Depending on your target audience, old browsers might be a major problem (China), but the browser landscape is rapidly improving in terms of a minimum expected set of features.