In IntelliJ IDEA, when I am editing an HTML file and open a tag for example <td> it will automatically add the closing tag </td> right after it.
I find this intensely irritating 98% of the time and only slightly useful the remaining 2% but I cannot figure out how to switch it off.
Navigate to Settings->Editor->Smart Keys
Uncheck “Automatically Insert Closing Tag” in the XML/HTML section.
In IntelliJ 15+, this has moved here (thanks @Philihp Busby):
Settings -> Editor -> General -> Smart Keys -> “Insert closing tag on tag completion”