Here is something to ponder. If you are on a level that requires the use of an external website for a solve, you may not need it.
Information changes, we all know this. Websites come and go and their information may become outdated or irrelevant. Sometimes they even get buried with newer, fancier websites that may not have the exact answer you seek.
If you come to such a level, I do my best to make sure the relevant information is always available. While I cannot promise this, if something is needed in a highly specific manner (chapter heading of a specific book format, or a list that may change next year, etc.) I attempt to make that information available within the level.
As an example, if you need a book/PDF in a specific layout to obtain the answer, that book or PDF is probably available in the same directory as the level. You may have to look for it, if it even exists, of course.
In my attempt to keep ACWoT stand-alone, I want to avoid relying on other sites as much as possible.
If you think you are on such a level, you can always PM myself or a moderator to find out if the resource is locally available.