Welcome to FR, Solaia. :) As others have indicated, the html sandbox is very helpful.
When you post an image, make sure that the source can be published or will appear (I’m not sure how to do that), otherwise you’ll get that little red box.
I think it has to do with proprietary rights of the website, whether or not it will allow images to be used, but I’m not sure.
Does anyone know if there is an option/setting to SUPRESS picture on FR? I sometimes take a peek at work on my lunch hour and breaks. FR is basically my go-to for news and such, but there are times that the pics are VERY work-inappropriate.