# User website preference is invalid with underscore

**URL:** <https://meta.discourse.org/t/user-website-preference-is-invalid-with-underscore/41784>\
**Category:** Support\
**Created:** [March 30, 2016, 6:14pm UTC](https://meta.discourse.org/t/user-website-preference-is-invalid-with-underscore/41784 "2016-03-30T18:14:39Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![pfaffman](https://sea3.discourse-cdn.com/meta/user_avatar/meta.discourse.org/pfaffman/32/120154_2.png) [@pfaffman](https://meta.discourse.org/u/pfaffman)\
**Post date:** [March 30, 2016, 6:27pm UTC](https://meta.discourse.org/t/user-website-preference-is-invalid-with-underscore/41784/2 "2016-03-30T18:27:23Z")

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> [@dGr8LookinSparky](#):
>
> Perhaps the underscore in the sub-domain is triggering the error?

That’s it. Underscores are not valid characters for hostnames.

> **[Hostname](https://en.wikipedia.org/wiki/Hostname#Restrictions_on_valid_host_names)**
>
> In computer networking, a hostname (previously nodename) is a label that is assigned to a device connected to a computer network and that is used to identify the device in various forms of electronic communication, such as the World Wide Web. Hostnames may be simple names consisting of a single word or phrase, or they may be structured. Each hostname usually has at least one numeric network address associated with it for routing packets for performance and other reasons.
> Internet hostnames may h...

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