Googles DoubleClick ad server for publishers went down for over an hour on Wednesday, bringing much of the internet to a standstill as pages failed to load, and potentially costing businesses millions of dollars in ad revenue.

Brian OKelley, CEO and co-founder of adtech company AppNexus told Business Insider that the outage likely cost publishers “$1m per hour” collectively in lost advertising revenue, without accounting for the losses from pages not loading due to the issue.

The problem first arose around 2pm GMT, and lasted for just under two hours, with much of the internet existing in a rare, ad-free status for the duration of the outage. Sites affected by problems included Forbes, The Wall Street Journal, The Guardian, Mail Online and Mashable.

Google is estimated to hold a 31.45 per cent market share of the global digital advertising sector, demonstrating how much of an impact even a small outage can have. Google stated that a software bug was the cause of the problem, and that it was working to ensure that it didnt happen again.

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