How to change an Image in Firebug

[Raifod]

I'm learning CSS and wanted to change an image on a site using Firebug. 

Initially I placed the image in my DropBox folder and I shared the link. Pasted the link (as attached), but it didn't seem to work. When hovered over the new url it stated " Fail to load the given URL'

I don't have a public folder in my dropbox as i downloaded it post 2013 and that facility has gone.

Any ideas?

Many thanks

[Sebastian Zartner]

Three things:
The image is not displayed because the link to the file is not valid. It is missing the protocol.
Also the URL you used for the image, which is shown in the screenshot, is not the address of the image itself but of a page showing the image. As far as I can see Dropbox doesn't offer permanent links to the actual files.
Furthermore note that Firebug works on the client side. It doesn't make changes on the server side. This means after a reload the changes you made in Firebug are gone and the original page is shown again.

Sebastian