Neiman Marcus shoppers hoping to scoop up Black Friday deals were instead greeted with an error message, which the company appeared to correct on Saturday as shoppers hunted for bargains.
According to Catchpoint Systems, which monitors retailers' Web performance, the luxury brand's homepage went down early on Friday, and was unavailable for much of the day.
It represented the first significant outage of the crucial Black Friday shopping holiday, and follows a smooth day of Web performance on Thanksgiving, according to Catchpoint.
On Saturday, Neiman tweeted that the site was back up, and that the retailer's had extended its sale due to the technical difficulties. Yet a few users were still experiencing trouble processing their purchases.
Catchpoint monitors desktop and mobile sites for the top 50 e-commerce retailers from 23 locations across the U.S.
According to its data, Newegg and HP experienced notable slowness with their desktop sites, with Jet.com experiencing the same issue on both its desktop and mobile sites.
A spokeswoman for Jet.com said the site's speed has been stable all day, and with the exception of a minor mobile blip on Thursday, the site is "is running faster due to some recently released improvements over the last couple of days."
Problems with Newegg's site escalated during the afternoon, and it was completely down from 11:30 a.m. to 12:15 p.m., according to Catchpoint.
Foot Locker's mobile site also faced intermittent slowdowns or errors, Catchpoint said.
Newegg, HP and Foot Locker did not immediately respond to requests for comment from CNBC.