This section is non-normative.
User agents that do not support MathML may decide to render the fallback content provided by the altimg* attributes in some situations e.g. when they are specified or under a preference option. In that case, an approximate implementation is to render the math element as a HTML img element with the value of altimg as an src attribute, the value of alttext as an alt attribute, the value of altimg-width as the CSS width property, the value of altimg-height as the CSS height property and the value of altimg-valign as the CSS vertical-align property [HTML5] [CSS2]. Here is a partial implementation using the attr() function of [CSS3Values]: