The ShippingPass pilot program launched last year and offers free shipping on all orders.
The retailer topped both Internet Explorer and Firefox consistency tests last month.
Dell.com had the best consistency score for Internet Explorer testing among large retailers tested in June, says Compuware Gomez. Last month, the retailer had the most consistent Internet Explorer site loading time with a variation of only 0.37 seconds. Dell also had the best Firefox consistency score at 0.38 seconds. The lower the variation, the more consistently the site loads.
Costco.com (0.72 seconds) placed second in Internet Explorer tests. Target.com (0.77) came in third, Amway.com finished fourth (0.88) and LLBean.com (0.91) fifth.
In Firefox testing, Costco.com came in second behind Dell.com with a deviation of 0.72 seconds. Walmart.com was third (0.79), Amway.com fourth (0.86) and LLBean.com and Overstock.com tied for fifth (0.88).
The average Internet Explorer consistency score among the 22 retailers measured in June was 1.74 seconds. The same group of retailers produced an average Firefox score of 1.61 seconds.
The consistency ratings take into account differences in the speed of web page delivery across multiple visits.
Click here for the full test results.