SharePoint Naming limitation in site names, folder names, and file names

This article lists the characters that you cannot use in the following names in Microsoft SharePoint:

• Site names
• Folder names
• Server names
• File names

Site names, sub-site names, or site group names

You cannot use the following characters anywhere in a site name, in a subsite name, or in a site or Active Directory group name:

• Tilde (~)
• Number sign (#)
• Percent (%)
• Ampersand (&)
• Asterisk (*)
• Braces ({ })
• Backslash (\)
• Colon (:)
• Angle brackets (< >)
• Question mark (?)
• Slash (/)
• Plus sign (+)
• Pipe (|)
• Quotation mark (")
• You cannot start a site name, a subsite name, or a site group name with an underscore (_) character or with the period (.) character.
• When you create a site name, a subsite name, or a site group name, you cannot use strings that were already used to name managed paths.
• You cannot use the period character consecutively in the middle of a site name, a subsite name, or a site group name.
• You cannot use the period character at the end of a site name, a subsite name, or a site group name.

Folder names

You cannot use the following characters anywhere in a folder name or a server name:

• Tilde
• Number sign
• Percent
• Ampersand
• Asterisk
• Braces
• Backslash
• Colon
• Angle brackets
• Question mark
• Slash
• Pipe
• Quotation mark
• You cannot use the period character consecutively in the middle of a folder name.
• You cannot use the period character at the end of a folder name.
• You cannot start a folder name with a period character.
• If you use an underscore character (_) at the beginning of a folder name, the folder will be a hidden folder.
• Additionally, a folder that contains the string "_vti_" is reserved by SharePoint, and isn’t supported.

File names

You cannot use the following characters anywhere in a file name:

• Tilde
• Number sign
• Percent
• Ampersand
• Asterisk
• Braces
• Backslash
• Colon
• Angle brackets
• Question mark
• Slash
• Pipe
• Quotation mark
• You cannot use the period character consecutively in the middle of a file name.
• You cannot use the period character at the end of a file name.
• You cannot start a file name by using the period character.
• If you use an underscore character (_) at the beginning of a file name, the file will be a hidden file.
• File names and folder names may not end with any of the following strings: 
• .files
• _files
• -Dateien
• _fichiers
• _bestanden
• _file
• _archivos
• -filer
• _tiedostot
• _pliki
• _soubory
• _elemei
• _ficheiros
• _arquivos
• _dosyalar
• _datoteke
• _fitxers
• _failid
• _fails
• _bylos
• _fajlovi
• _fitxategiak
• In addition, file names and folder names cannot start with the “_vti_” string, such as the followings:
• _vti_cnf
• _vti_pvt
• _vti_bin
• _vti_txt

MSDN Link: https://support.microsoft.com/en-us/kb/905231