# The “headers” attribute on the element “th” refers to the ID X, but there is no “th” element with that ID in the same table.
> Canonical HTML version: https://rocketvalidator.com/html-validation/the-headers-attribute-on-the-element-th-refers-to-the-id-x-but-there-is-no-th-element-with-that-id-in-the-same-table
> Attribution: Rocket Validator (https://rocketvalidator.com)
> License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/)
Every ID in the `headers` attribute of a `th` has to be the `id` of another `th` in the same table, and the validator flags each one that isn't.
On a header cell, `headers` ties a sub-header to the header cells above it or beside it. When a "Sales" header spans the "Q1" and "Q2" columns, `| Q1 | ` says that Q1 belongs to Sales. The value is a space-separated list of IDs, and the validator checks each one on its own, so a single cell can trigger this message more than once.
The referenced header is usually where things went wrong. The validator reports the ID when:
- the group header has no `id`, or a different one (IDs are case-sensitive, so `Sales` doesn't match `sales`)
- the `id` sits on a `td` styled to look like a heading, or on the `tr`, the `thead` or a `span` inside the `th`, instead of on the `th` itself
- the `th` with that `id` belongs to another table, like a nested table or a separate table used as a fixed header row
Screen readers rely on these references to tell users which headers a cell falls under. When an ID doesn't resolve to a `th`, the sub-header loses its link to the group. Put the `id` on the group header's `th`, changing a `td` into a `th` if needed. If that header no longer exists, remove its ID from `headers`.
The standard also forbids a header cell that targets itself, either directly or through a chain of other headers' `headers` attributes. The validator doesn't report that loop, so check for it yourself when header cells point at each other.
## Invalid example
```html
```
## Valid example
```html
```