I have a trouble with tooltip. It doesn't show up

Question

Tooltip doesn't show up. I've tried to display it with
<span id="error-dropdown">Here is error text</span> and opacity property in CSS, but it doesn't display anyway. Link

<img src="https://symboldev.pp.ua/_data/error-sign.svg" alt="Error" id="error">

#error {
    height: 30px;
    width: 30px;
}

#error::after {
    content: "Here is the tooltip text";
    display: block;
    width: 300px;
    height: 300px;
    background: #555;

    position: absolute;
    visibility: hidden;
}

#error:hover::after {
    visibility: visible;
}

Answer 1

Here's a solution - just wrap a link around the image.

#error {
	height: 30px;
	width: 30px;
}

#error::after {
  content: "Here is tooltip text";
  display: block;
  width: 300px;
  height: 300px;
  visibility: hidden;
}

#error:hover::after {
	visibility: visible;
}

<a href="" id="error"><img src="https://symboldev.pp.ua/_data/error-sign.svg" alt="Error" id="error"></a>