• by Gavin O'Malley  @mp_gavin, July 6, 2009

Fast load-time; no fancy Flash animation; well-placed contact information; clearly priced seasonal product purchases one click away. For whatever reason, flower e-tailer ProFlowers.com successfully "converted" a higher ratio of visitors -- a staggering 38.6% -- than any other ecommerce site in May, according to new data from Nielsen.

Complicating matters, rival 1800flowers.com -- which appears to be nearly identical to ProFlowers.com -- ranked Number 8 on Nielsen's list with a more modest 20.5% conversion rate.

One reason for the divide might be found in Nielsen's list of top ecommerce advertisers in May, where ProFlowers came in Number 3 with 1.4 billion online ad impressions -- nearly 100% of which were display ads -- while 1-800-Flowers didn't even make the list.

For the record, eBay topped that list in May with approximately 2.5 billion online ad impressions -- about 28% of which were sponsored search ads.

Overall, apparel and accessories was the leading product category with 11.2 million purchases, representing 15% of all online purchases in May, according to Nielsen. Apparel and accessories buyers spent an average of $90.31 each during the month.

Not far behind, home and garden ranked Number 2 with 8.8 million purchases, which represented 12% of all ecommerce in May. Buyers in that category spent an average of $109.69 each.

Ebay was the leading online retailer in the home and garden category with 1.9 million purchases, representing 21% of all home and garden purchases in May. EBay home and garden buyers spent an average of $54.01 each during the month and made 1.87 purchases each.