The five best online April Fools' pranks

2. Opera reads your facial expressions

Also in 2009 – a good year for tech pranksters – Opera rolled out a browser that promised to read your facial expressions, and respond accordingly. Which sounded awesome, because let's face it – who doesn't want to click to the next blog with only a smile and a wink? Of course, as Opera reps noted, the software was by no means perfect.

"Face Gestures is compatible with most types of facial hair and haircuts. But if your face is covered with more than 25% of facial hair, recognition errors may occur. Please note that handlebars and goatees are compatible independently but if combined recognition will decrease," read a blog post introducing the browser. "At the moment soul-patches crashes the browser and it refuses to relaunch, we are looking into this problem."

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