Which of the following is NOT a common accessibility error found on web pages?

HubSpot’s accessibility guidance highlights common problems such as missing form labels , missing alt text , and insufficient color contrast because these directly block access to content or controls. A missing specific heading level is different because accessibility depends on a logical heading structure, not on the presence of one exact tag. An interface can be fully accessible without any h4 elements if the document outline remains meaningful and sequential. The issue is improper heading hierarchy, not the absence of a particular heading level by itself.