unknown window that can't close

I get a window on the display with no indication of where or what program
started it. the page simply says "Navigation to the webpage was cancelled"
on a banner. Further down it says "What you can try; -refresh the page".
Cliking this only produces a similar page (also with no close options)
telling me to check my internet OR the website is encountering problems OR
to check my typed address. This window has a date and a time in the menu bar
but no X to close or ability to minimize it or dialog box to close. The only
way i can get rid of it is to use Task Manager. this is getting very
tiresome as it happens quite often. Always the internet connection is
working and i don't believe it is my typing that many errors. Because the
window does not identify itself i don't know what website is causing this.
Has anyone any suggestions on how to eliminate this issue?
thank you for your help