I came upon something curious today. The following code is in a file in a public_html folder. I expected the first paragraph to display a broken image, but both images showed fine. I checked in three browsers.
The only thing I could come up with is that the browsers are ignoring the ../ in the first paragraph since the file is already in web root.
I tried to Google it to see if it was documented, but could find nothing. I could swear I've accidentally added a ../ to an img src in a public_html file before and got a broken image.