Over at Math.SE we decided to merge two tags into one and give it a combined name. After reading up on the character number limit and the allowed characters in tag names, we decided to rename our new tag (examples+counterexamples), since it is a tag about, well, examples and counterexamples.

Great, now I go to the Math.SE tags page and type in the search box "examples" and I see our spanking new tag.

Now I think: hey, let me edit the tag wiki for it, and see what questions are now tagged under it! So I clicked the link... and it doesn't take me where I want it to. How am I suppose to access the tag wiki then?

  • BTW: it looks like the + character is interfering with how the system parse a request to see questions simultaneously using two tags. If this is the intended behaviour, can someone from the SE team rename that tag to (examples-counterexamples)? Aug 18, 2011 at 15:33
  • It's pretty clearly intended, goint to tags/homework+calculus shows questions tagged both homework and calculus for example. Escaping the + to %2B doesn't work either, so your proposed change for the tag is a good idea; they should also auto-convert + to - when a tag is created, or something.
    – user154510
    Aug 18, 2011 at 15:38
  • It is interesting that this does not seem to affect trailing + as in the c++ tag, or I'm sure we'd have heard about this long ago.
    – hammar
    Aug 18, 2011 at 15:46
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    There's all sorts of stupid breakages related to c++, actually, now that I went and looked for them. Try the following links: stackoverflow.com/questions/tagged/c++0x+c++ stackoverflow.com/questions/tagged/c+++c++0x stackoverflow.com/questions/tagged/c%23+c++ stackoverflow.com/questions/tagged/c+++c%23 Aug 18, 2011 at 15:52
  • But on stackoverflow apparently one can use a space to concatenate tag names: http://stackoverflow.com/questions/tagged/c++ c%23 which is how the links from "related tags" are created when you access the page for questions tagged as (c#) or (c++), which would then prevent the breakage. So perhaps a certain workaround is hardcoded for SO? Aug 18, 2011 at 15:55

1 Answer 1


Stop doing that! I fixed it in the database to [examples-counterexamples] (search and such will index in the next 15 minutes).

Obviously there's a gap in the merge screen that allow this through, we'll get around to fixing this rare case.

  • 1
    So is + actually a disallowed character? (If so maybe Jeff should edit his answer in that linked question.) Aug 18, 2011 at 15:57
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    @Willie - In the middle of a tag, yes...this isn't really supported. I updated the post in question to eliminate the confusion over the rules here. Aug 18, 2011 at 16:04
  • Is there an error message presented upon attempting to use such invalid characters in a tag name? If not, have you considered adding such a thing? Most people doing this probably haven't read Jeff's official rules. Aug 19, 2011 at 4:59
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    @Cody - this can only happen via the moderator merge screens as far as we're aware...you can't do it through normal user UI means. We will add a message to the mod screens through, just very busy at the moment, you'll see why soon :) Aug 19, 2011 at 10:00

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