You may have a slow connection, excessive latency or the Yahoo! site may be overloaded at the time when you connect. It's also possible that your ISP may be throtling down some sites for whatever reason, and the Yahoo domain may be in that list.
In the lats few days, I've experienced some slowdown on Yahoo, but not close to as severe as what you mention here, only about 15 to 20 seconds delays, and only when using Chrome.
Is it only the Yahoo! mail site that is slow, or every / most page you load is slow?
Try logging in at another time of the day.
Try contacting the customer's service of your ISP to see if there is a problem with them.
Electro, March 2012
