Lighting bolt icon

When going to the given URL (http://aridorlaw.dos-commas.com/%D7%9E%D7%94%D7%A2%D7%99%D7%AA%D7%95%D7%A0%D7%95%D7%AA/) – ON MOBILE
and click the first tab, there are some articles. Some of them linked to post page and some to outer sources. The ones with the outer sources links have this lightning bolt icon. Why is that? how can I get rid of it?

The page I need help with: [log in to see the link]