The Zotero Connector senses information on webpages through site translators, and the save button in the browser toolbar will feature an icon for a given type (book, newspaper article, etc.) if a site translator recognizes the page being viewed:
On all other webpages, the Zotero Connector will display a gray page icon:
You can hover over the button to see which translator, if any, Zotero will use to save the page.
Zotero's translators should work with most library catalogs, popular websites such as Amazon and the New York Times, and many gated databases. If a site isn't currently supported or a translator isn't working, you can still click the gray icon to save basic information from the page to your Zotero library, but you may need to fill in some details that Zotero couldn't automatically detect.
If you see only a webpage icon on Amazon product pages or NY Times articles (not the home pages), see Troubleshooting Translator Issues.
If you see an item type icon on Amazon product pages and NY Times articles but see a webpage icon on another supported site, you can report it in the forums. Be sure to provide an example URL.