I have been developping for some time a character sheet where I want to put a lot of icons, and I had not bothered yet to put them on the Github repo. I was working with temporary icons found online, with the idea at some point to upload a nice set of Creative Commons icons on the Github repo. In the meantime, to be ready to make this update and have all at the same place in the CSS? I had created a serie of classes with URL .sheet-icon-agressive{ content : url(<a href="https://s3.amazonaws.com/files.d20.io/images/19/Vp6EsSd3aGqqL78ZPmw1WQ/max.png?1575370629" rel="nofollow">https://s3.amazonaws.com/files.d20.io/images/19/Vp6EsSd3aGqqL78ZPmw1WQ/max.png?1575370629</a>); } /*License Information*/ with a <span class="icon-agressive"></span> I had my image display in the span with no issue. I had already noticed that some of the CC icons I as selecting as temporary were not always working, but didn't bother as it was temporary. Now, I have finally an upload of the icons, and I was looking to update all these .sheet-iconXXXX classes but it doesn't work. If I change the class to, the span doesn't display anymore .sheet-icon-agressive{ content : url(<a href="https://raw.githubusercontent.com/ChrisDDickey/roll20-character-sheets/Earthdawn-Images/Earthdawn%20(FASA%20Official)/Images/Agressive.png" rel="nofollow">https://raw.githubusercontent.com/ChrisDDickey/roll20-character-sheets/Earthdawn-Images/Earthdawn%20(FASA%20Official)/Images/Agressive.png</a>); } I thought it could be something wrong with the way Github is hosting, but the same url used with img works just fine <img src="<a href="https://raw.githubusercontent.com/ChrisDDickey/roll20-character-sheets/Earthdawn-Images/Earthdawn%20(FASA%20Official)/Images/Agressive.png" rel="nofollow">https://raw.githubusercontent.com/ChrisDDickey/roll20-character-sheets/Earthdawn-Images/Earthdawn%20(FASA%20Official)/Images/Agressive.png</a>"> currently 57 such classes and 159 instances in my HTML !! God help me (yes I'll call "god" whoever explains me the difference between {content: url()} and having the actual <img src=""> as I can't see any sensible explanation on this by google searches