HTML Guide for nesting
The <iframe> HTML element represents a nested browsing context, embedding another HTML page into the current one.
As the iframe is a container that holds an embedded HTML page, it cannot be nested inside an a tag.
An <input> tag can’t be used inside an <a> tag.
A <label> tag can’t be used inside an <a> tag. Consider using other tags like <span>.
A <label> element cannot contain other <label> as a descendant. Check for nested elements or closing tags that may have been misinterpreted, for example:
<label>name</label></label>
The <caption> element specifies the caption (or title) of a table. It’s not allowed for a <caption> to contain another table.
A <textarea> tag can’t be used inside an <a> tag.