I might try putting *.yahoo.com into the Trusted sites list to see if its just the security settings causing that.

Internet Options / Security tab, highlight the Trusted sites,, the push the Sites button.

I tried the above, putting in the yahoo.com into the trusted sites. A screen came up saying that only sites with the https. could be put in there. Although there is a http.yahoo.com in there now....so that is something for me to ponder over. Also at the top toolbar, way up in the right screen is a icon? that shows activity when going to a site, or opening mail. That seems to be dead, it never moves, just stays a very light gray color. I do have a gmail account, that I use for my medical, and that is working normal. It is the yahoo one, it seems to be stuck.
Any help would be appreciated.
Darlene

On the window under the list of safe url's is a check box you can uncheck that changes the rule for that message you received for the Only HTTPS sites allowed there.

Mikie, thanks for trying to help. I have done all that you said, and still nothing. I can open the email by right clicking and read in another window. It refuses to use the mouse to open anything. Plus I cannot compose a letter. I notice that the round icon ? at the right top of the top bar after the browser name is not active, it is a light gray, when normally you click on something it turns a dark gray, and then goes around like a clock until the page opens. Another thing I have noticed, that at the top of the emails page, is a orange sign that says "loading yahoo browser bar". I never installed it, and use the classic yahoo. The less stuff I have on my pc, the better. I finally decided maybe that is it, tried to download it, and when I click download, nothing happens. Guess I have to have the thing go to the shop. Thanks again.
Darlene

Maybe look in event viewer and look for red x errors at and after last reboot. Some if you follow the link even will suggest fixes.

Its odd that its both firefox and ie & only yahoo you seem to have the trouble.
Maybe in control panel, Java .. perhaps clear both cache's and I would assume you have cleared your internet cache's.

Another thing to try is to run checkdisk (R-click C-drive, tools) or ;
chkdsk /f
and at boot it will run error checking on the disk and file system.
And you might also try system file checker from boot too, you may or may not be able to use it .. from the run line or open a cmd window .
SFC /ScanOnce
i think. I forget XP exacts so cmd window is better as it will show success/error for the command ... it will run at next boot.

What service pack level on xp ? perhaps reinstall if that is an option with the SP#.

Bout all I can think of at the moment. Hope Error Logs show the problem. Then you have something to go by.