That means etither you typed the URL wrong, the owner of the texture doesn’t want you using it, or in general it means that the computer has understood and recieved you’re request but can do nothing about it.
Okay so @DevJolly, you’re actually incorrect on this one. At the end of the error message it has
HTTP 403 (Forbidden)
Which is the error message that happens when a moderator rejects a file from being added to Roblox. This is the case with Images such as Ads, Images that you upload to the site, and also images you upload through the studio. This also applies to scripts, which are automatically checked by Roblox’s script detection service which automatically goes through scripts, looking for things that are against the Roblox ToS or appear to be anything that might scam a player or be inappropriate. Once more, this also applies when things are imported from third-party applications such as C4D or Blender as MeshParts or as MeshID’s. Every time something is uploaded, it’s checked by a moderator. If it’s seen as breaking the rules of Roblox, it’s then marked as (Forbidden) and the asset is rejected, and will not be able to be loaded or used in any way.