Mary's laptop technician put in an ad blocker with her browser, and now she's being bothered to turn it off every time she visits Yahoo. Leo says a lot of websites now are seeking to get her to stop using the blocker in order to get paid by ads. So they want her to unblock them in order to see their ads. Chances are, that the browser has an extension. There should be a way to "white list" the yahoo page so that popup will stop occurring.
Joesph is getting popups. Leo suspects that there's adware installed on his computer, and you can go through add/remove programs to uninstall whatever you don't recognize. Look for browser extensions, as well. You can also run the Windows Malicious Software Removal Tool and Windows Defender to get rid of any malware.
Kristi is having trouble with Firefox loading. Leo says it's likely a problem with an extension. She should start up Firefox without the extensions, and it's likely it'll start right up. If it does, then she'll know it's a bad extension. Would that also cause Java not to work? Leo says that no, that's a separate issue, and every browser has a "Disable Java" option. Another thing to try is resetting Firefox with this how-to at tomsguide.com.