What Is This?

See the attached screen-shot of my What Is This issue.  I use WIN 8.1 and IE11 and have seen this interrupt my browsing a few times now.  Of course, I do not call the telephone number or click on any hypertext, but it does freeze IE11 so that I have to use Task Manager to quit internet explorer.  I've run full scans with my Norton and it doesn't find anything.  Not surprising.  Any explanation or help would be appreciated.