Marker.to is a simple and quick annotation tool which allows you to use a marker pen on web pages. Have you ever used highlighter over paper documents? It is as same as that but here it works online for web pages. Using this tool you can highlight important parts of any online news, post, article etc to share it with your friends so that they can easily find the lines you want to show them.
It provides you browser extension & bookmarklet which you can install from its home page and then run its marker just by clicking its icon (bookmarklet) and you can highlight any text on any website with your mouse.