Java Script Hacks

What are the most interesting HTML/JS/DOM/CSS hacks that most web developers don’t know about?

The best JavaScript code is the code that doesn’t need to be written at all.


define “hacks”.

Are you trying to find out about vulnerabilities that have been exploited?
Are you trying to find out about coding tips?
Or Are you trying to get us to write your next 10-things list for you to run off and slap on every link-farm ‘check out my latest article - number 7 will surprise you’ by copy-pasting from a web forum because ‘life hacks are popular’.