Pinpointer by Rumperuu

Pinpointer is a browser extension that allows you to create and share links to arbitrary elements on a webpage.

You select a page element and click the extension icon to fine-tune your selection and generate a link, which you can then share. For someone without the extension, the link will work as normal and just take them to the page, but someone with the extension will have the selected element focused on and highlighted for them.

As an example, try this link before and after installing the extension.