Headings
Headings should be used to create an outline for the content found within the page/post.
Improper Heading Level
The above heading was improperly used because it skips from the "Headings" heading level 2 to a heading level 4. This heading should be a heading level 3, and then if the size/format doesn't look right it should be modified via CSS (though this has generally already been addressed by the site theme).
Another Heading Level
The above heading is actually used correctly because it is the same level (one level lower would have been acceptable too) as the heading that precedes it, thus it didn't skip a heading level.
Images
Content Image
The above image has no alt attribute describing the content of the image. All content based images, with no adjacent text describing the picture, need an alt attribute.
Background Image
The above image is a background image that should be used purely as decoration (design) and thus needs no alt attribute and in fact cannot have an alt attribute.
Color
The heading above (being 18px or larger, or 14px or larger and bold) must have at least a 3:1 contrast ratio.
This text, being small/regular sized text, must have at least a 4.5:1 contrast ratio.
There are times that placing text on top of an image is necessary as part of the design, however adequate contrast between the text and the image must be ensured.
The contrast between this background image and this text is not adequate.
Note that the Accessibility Checker did not flag this for inadequate contrast because it's comparing the text color with the light gray background color, so always double check text on top of images and use your own judgement.
Links
Has No Context
It's common to need to place links inline within text, however the link text must make sense outside of the context of the surrounding text, such as click here.
Has Context
Instead the link text should have context on its own, such as read more in our Links Guide.