Well it looks like Douglas Crockford just made a whole lot more people switch to JSHint. Have a look at this commit.
The “Mixed spaces and tabs” error has been removed, and a new “Use spaces, not tabs” error has been added in its place. Aside from that, there’s one tiny change in that diff that shows the cause of this. The following line (comment added):
at = source_row.search(/ \t/);
// ^ Space
has been replaced with this:
at = source_row.search(/\t/);
// ^ No space!
Following that search there’s an if statement. If the condition evaluates to true, the “Use spaces, not tabs” warning is issued. Here’s that statement:
if (at >= 0) {
warn_at('use_spaces', line, at + 1);
}
I hope that this is just a little oversight by Crockford. As you can see, JSLint is now going to raise this warning if you use a tab character anywhere. Unfortuately, his commit messages are completely useless, and the documentation doesn’t appear to have been updated, so I can’t do anything other than speculate as to the reasons behind this change.
I suggest you abandon JSLint and switch to JSHint right now.