Accessibility plays a vital role in web development. Our users can be limited to a keyboard, they might be using a screen reader, or could be color-blind. Making sure that our users are comfortable in all scenarios is the key to making a good site. Similarly, creating a good Web Component also includes making a Web Component accessible. 

When you are creating a Web Component, you need to make sure that your Web Components are accessible at least up to a certain extent. For example, an image should always have alt text. A link should always have alt text. Input fields should have proper aria-labels. There should be sufficient color contrasts. Tab orders should be in the correct order, and so on. 

Now that we know what can be done to make a component accessible, let's take a look at a small example. Let's say the requirement is to create a <header-image> component that shows a full-width image. In order to make sure that this component is accessible, the image used should have alt text. 

Let's take a look at our getTemplate() function for this component:

getTemplate() {
  return `
    <img src="${this.getAttribute('src')}" 
         alt="${this.getAttribute('alt')}"/>
    ${this.handleErrors()}
    <style>
      img {
        width: 400px;;
      }
    </style>
  `;
}

Here, we are adding an alt attribute to the image tag, and we are grabbing this alt text from the Web Component itself:

<header-image alt="Blue Clouds"
      src="clouds-sky-header.jpg">
</header-image>  

We also have an error handler function called handleErrors(), which makes sure to tell the user that the component is missing alt text:

handleErrors() {
  if(!this.getAttribute('alt')) {
    return `
      <div class="error">Missing Alt Text</div>
      <style>
        .error {
          color: red;
        }
      </style>
    `;
  }

  return ``;
}

This will show a Missing Alt Text error message in red, when the component is missing the alt text. We can solve other accessibility issues in the same way.