HTML Guide

Bad value “X1,Y1,X2,Y2” for attribute “coords” on element “area”: A circle must have three comma-separated integers. The first integer must be less than the third. A polyline must have at least six comma-separated integers.

The coordinates specified for an <area> element using the coords attribute are not in a valid format.

For a rectangle (shape="rect"), the format X1,Y1,X2,Y2 is expected, where the top-left corner is specified by X1, Y1 and the bottom-right corner is specified by X2, Y2, therefore X1 must be lower than X2, and Y1 must be lower than Y2 because the coordinates 0, 0 start at the top-left.
For a polygon (shape="poly"), the format X1,Y1,X2,Y2,...,Xn,Yn is expected to contain a list of coordinate pairs (at least 3, for a triangle).
For a circle (shape="circle"), the format X,Y,R is expected where X, Y represents the coordinates of the center of the circle (from the top-left corner), and R is the radius.

Learn more:

HTML Living Standard: the area element

Related W3C validator issues

Bad value “http://” for attribute “href” on element “area”: Invalid host: empty host.

An href attribute with the value http:// is not a valid URL because the host section is missing.

The href attribute in the area element must contain a valid URL. A URL requires a scheme (http or https), followed by ://, and then a valid host (such as example.com). The value http:// lacks a host, making it invalid according to URL standards and resulting in a validation error. If you don’t want the area to navigate anywhere, you can use href="#" for a placeholder or omit the href attribute entirely. To link to an actual location, provide the complete URL, including the host.

Invalid example:

<map name="myMap">
  <area shape="rect" coords="30,23,183,191" href="http://" alt="" >
</map>

Valid example with a real host:

<map name="myMap">
  <area shape="rect" coords="30,23,183,191" href="http://example.com/" alt="" >
</map>

Valid example with a placeholder, no navigation:

<map name="myMap">
  <area shape="rect" coords="30,23,183,191" href="#" alt="" >
</map>

Replace http:// with a full URL or a suitable placeholder as needed for your application.

The “shape” attribute on the “a” element is obsolete. Use “area” instead of “a” for image maps.