Open in nbviewer
These are various options for opening your current URL in nbviewer with one click. They will work if you are looking at any URL that can be pasted into nbviewer.
All Browsers
Any browser can use the bookmarklet. Simply make a new bookmark in your browser and copy the code from nbviewer_bookmarklet.js into the URL field. Activating the bookmark will open a new tab pointing nbviewer at your current URL.
Chrome
Use the Chrome extension, which adds an nbviewer icon to Chrome's toolbar.
Firefox
Use the Firefox add-on, which adds an nbviewer icon to Firefox's toolbar.
Safari
Download and install the Safari extension.