Heath Ledger's shock death caused one of the biggest internet meltdowns since the death of Steve Irwin in 2006, with news sites and search engines experiencing huge traffic spikes.

The 28-year-old Australian actor was found dead on Tuesday in his New York apartment.

Unique browsers on smh.com.au rose almost 250 per cent compared with Tuesday's figures and total page impressions jumped 60 per cent, according to Nielsen NetRatings.