I want to determine more than one language for a document, because it's available in more than one language. If I use:

```
<meta http-equiv="content-language" content="en,de,fr" />

```

this is not W3C valid and the validator says I should define it in the root's `lang` attribute, but this attribute only supports one language:

```
<html lang="en">

```

works, but not

```
<html lang="de,en,fr">

```

So where should I define it?