I just joined the forum so I am not really sure if this is the place to ask this type of question:
FYI: I exchanged several emails with Bing Webmaster (BW) support and they could not help.
Anyway, BW is showing several URLs with 404. I copied one of the URLs and pasted it into my browser address bar and sure enough it returned a 404?
I pasted the same URL into Notepad++ and clicked on ANSI encoding. It revealed a hidden space in the url. Every 404 URL has a hidden space; sometime two hidden spaces.
Some URLs have 20 or 30 back-links so this concerns me.
Any thoughts? I apologize for the long-winded explanation.
My site has been active since 2006 and this is my first experience with the 404 errors due to hidden spaces in the URLs.