In web version Yahoo Mail, I randomly clicked on "Delete" (I thought I've selected one email but nothing was selected) and it showed a message "Are you sure you want to permanently delete 1072 emails?" and the "yes" was preselected as default!
If I didn't notice, I was going to delete all my years email history!

More Detail:
there was no email selected at all
I clicked on delete by mistake
a small window popped showing: "Are you sure you want to delete 1072 emails?" (I'm not sure about the exact words or the number, but that's not the point)
the preselected default button was "YES!"
I'm glad that I noticed and canceled it!
but if I accidentally was going to press enter, all my emails was gone!
Please fix this!