Although Zotero cannot automatically capture citation info from web pages, you can still add them to your Zotero library.
Click the button at the bottom of your browser to access the three-column Zotero panel. Then, click the "Save to Zotero (Web Page)" button save a link to the page.
This will save a new "web page" item to your library.
Zotero automatically captures a snapshot of the page if the default setting of "Automatically take snapshots when creating items from web pages" is enabled in the "General" section of the "Preferences" menu. Taking a snapshot saves a copy of the page to your computer. It includes the page's text and images as they were on the day you captured it, so that you can still be able to view your copy when offline or when the webpage has been removed.
If the snapshot preference is not toggled, you can select the snapshot option by clicking on the dropdown arrow the the right of the "Save to Zotero (Web Page)" button and selecting "Save to Zotero as Web Page (with snapshot)."