It seems that the root cause of this is that certain sites have something called a .htaccess hack. I traced down the problem to certain normal sites that I found through the Google search toolbar. Clicking on the sites takes me to a redirect to would-be malicious links (fortunately the domains no longer exist). Examples: www. metromanias. com wwww. peoriavascularsurgery. com etc. Just a shame that there is no way to report such sites...