When you define or assign tags in WordPress, here is what WordPress does:
1. Every tag must have a name.
2. Every tag must have a slug, the url of the tag.
3. By default, WordPress will automatically generate the tag slug based on the name of the tag you entered.
4. However, if either the value of the tag name or the tag slug is new, then WordPress will consider it is a new tag in the system.
So, a problem will arise, when your blog has non-western language characters or terms been used as tags. (more…)