Hi Kristin,
Simply rename a worksheet tab with something that includes at
least one invalid character, one such invalid character is backslash
and you get a list of invalid characters
characters not allowed in sheetnames
: \ / ? * [ or ]
colon, back slash, forward slash, question mark, left and right square brackets.
Sheetnames may be up to 31 characters in length.
Most of the characters Richard gave as example are valid,
the forward and backard slashes are not valid, but the
period, left and right parens, dollar sign, commercial at sign,
and ampersand are all valid.