The Costco Wholesale Corporation (COST  ) has suffered a costly setback after a series of website outages on Thanksgiving and early on Black Friday cost the company an estimated $11 million in lost revenue.

Holiday shoppers hoping to cash in on Costco's pre-Black Friday deals were met with warnings that the website was experiencing lengthy delays. For some, the website took excessive amounts of time to load, while for others, it was unable to load at all. The heavy load on Costco's servers caused issues for roughly 16 hours, which cost the company dearly during one of the busiest online shopping days of the year.

Retail aggregator LoveTheSales.com calculated the approximate losses suffered by Costco to be approximately $11 million based on calculations made using the company's year-end financial reports. Costco has yet to release its own estimate, nor has it addressed the incident at all. Despite numerous attempts by the media to contact Costco for a statement on the outages, the retail giant has remained silent. Costco has, however, addressed the outages by extending its Thanksgiving sale into Black Friday.

While Costco's losses were certainly the highlight of the day, the wholesale chain was far from the only company to experience technical issues due to high website traffic. H&M (STO: HM-B) suffered brief outages lasting five minutes on Thanksgiving morning and suffered intermittent outages throughout Black Friday. Home Depot (HD  ) also suffered slow load times throughout Thanksgiving, but no total outages were reported.

While Cyber Monday is when retailers typically roll out their biggest online deals to attract shoppers to their digital storefronts, companies have been holding sales well in advance of the digital "Black Friday" to maximize on the incomparable popularity of online shopping. Given the sheer volume of shoppers on Black Friday and Cyber Monday, and the growing traffic to online retailers are holiday sales are expanded, outages are to be expected. While most e-commerce retailers anticipate website outages, some have admitted that they lack contingency plans for such an event. Even industry veterans such as Amazon (AMZN  ) have suffered outages.

Regardless of outages, Black Friday was still a massive success, with retailers raking in $7.4 billion in online sales alone. The average order per shopper was $168, setting a new Black Friday record. In general, online sales jumped 20% from last year.