`fieldset` must have one `legend`

Rule ID	Control 8
Definition	Every `fieldset` element must contain exactly one `legend` element.
Purpose	Multiple `legend` elements contained in the same `fieldset` may result in the improper calculation of labels for assistive technologies.
Mappings	HTML4 Legacy Techniques (Required) HTML5 and ARIA Techniques (Required)
WCAG Success Criteria	3.3.2 Labels or Instructions (Level A, Primary Success Criterion) Other Related Success Criterion: 1.3.1 Info and Relationships (Level A) 2.4.6 Headings and Labels (Level AA) 4.1.1 Parsing (Level A)
Rule Category	Forms
Scope	Element
Target Resources	`fieldset` and `legend` elements `fieldset`
Techniques	A `fieldset` element should have one and only one `legend` element to describe the purpose of the form controls it contains.
Informational Links	HTML 4.01 Specification: Adding structure to forms: the `fieldset` and `legend` elements W3C WAI Accessibility Tutorials: Forms Concepts H71: Providing a description for groups of form controls using fieldset and legend elements H88: Using HTML according to spec

fieldset must have one legend