I saw a telling about a red block. Hee said it was never used, and I want to know how he got it. Can anyone explain?

It is a block that was from previous versions of Scratch, these ‘'red blocks’' have been removed, however, these project with these can be opened here, which results in a red block.

If it said obsolete! Then it was a REALLY old block (I think), if it said *stretch* then it was from Squeak, the language 1.4 is written in.

The user id block is obsolete and shows up red in older projects. That was a new obsolete block and survived only a few days before removal due to errors in the system which would cause Scratch 2.0's release to be pushed back even farther. Sometimes the code for these blocks still works (such as the user id block). Lots of blocks still exist on the wiki, even if they don't exist here. I think there's a list of no longer used blocks on the wiki.