Solve intermittent issue with my website

Avg Bid (USD)
Project Budget (USD)
$30 - $250

Project Description:
My website gets an intermittent error from time to time. It seems to be confined to the main page and some product pages. The error reads:
Fatal error: Call to undefined function mssql_connect() in D:\Hosting\8997993\html\includes\[url removed, login to view] on line 13

Other times, it seems to work fine. When I look at the google webmaster tools dashboard it warns me of "possible outages".

My website is

Thank you

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