Some old amateur gardening and houseplant sites mostly linked to pictures that don’t exist anymore. There are other reasons too. Some were always just worthless. Is there anyway to tell Google not to bring up a site again?
If you’re doing a search, you can use site:foo.com to restrict the search to the specific site foo.com. So by prefixing that with a minus sign, you can exclude the site from your search. For example
"cecil adams" -site:straightdope.com
finds the name “cecil adams” on all sites except straightdope.com.
There was a Firefox extension for this very purpose . I stopped using it since the little green addition beside each search giving such options was clutter to me. Plus I didn’t use it enough.
Still, Mozilla appears to be dumping extensions anyway.
Google has its own “Personal Blocklist” extension, if you use Chrome.