Can’t make a pop-up appear with thumbnail nor link (ArcGIS Online)

Can’t make a pop-up appear with thumbnail nor link (ArcGIS Online)

I'm trying to enrich my web map by giving pop-up to a layer with a thumbnail with link to larger picture.
I've uploaded two files up to my AGOL account. I'm looking to use those files as pop-ups in a service layer.
I've manged to open them via the 'My Content' GUI. Still I could not open them when copy-pasting the url as an attribute and then using it as a pop-up
I think the problem is some how related to the url's suffix: when a file extension is included the pop-up appears OK(*.jpg); when the url don't contain file extension suffix it doesn't appear.
How to make a pop-up appear with a valid url (for the thumbnail and a link)? 

Solutions/Answers:

Answer 1:

The problem was in the copy-paste procedure: when I copied the URL from the browser’s URL bar and pasted it directly to the field calculator, it some how got distorted; I think this happens because of encoding problem but I’m really not sure (hope if someone can comment on this).

The solution is a workaround: I copied the URL from the browser, paste it in the Notepad, copied it again from the Notepad and then paste it in the ArcGIS field calculator.

References