. 1"> Yahoo is second only to AOL in the list of top telecom/Internet services sites, according to Nielsen/NetRatings April ranking of unique visitors. But as far as free e-mail goes, Yahoo rules. Yahoo operates the Webs most popular e-mail service, with 40.4 million unique visitors to the service in April, according to Nielsen/NetRatings. Hotmail is in close pursuit, clocking in at 34 million unique users for the same period.But the archrival thats really behind Yahoos jerkily executed upgrade is Google Inc. In April, the uber search site filed paperwork for its greatly anticipated initial public offering, which was expected to raise as much as $2.7 billion.That same month, Google unveiled plans to offer 1GB of storage capacitythe equivalent of 500,000 pages of free e-mail per user through its Gmail service. That service is still undergoing testing. Columnist John Pallatto thinks that when it comes to Googles IPO, we should learn from past dot-com hysteria. Click here to read more. Yahoo has been busily trying to scrape Google out of its system for months: In February, it replaced Google Web search technology with its own. As of this storys posting, Yahoos site performance was still impaired. Editors Note: This story was updated to include a comment from a Yahoo spokeswoman and to correct Nielsen/NetRating figures. Check out eWEEK.coms Messaging & Collaboration Center at http://messaging.eweek.com for more on IM and other collaboration technologies.