We can perform basic accessibility checks by using tools such as Google's Accessibility Developer Tools (https://github.com/GoogleChrome/accessibility-developer-tools). We can inject the Google Accessibility testing library in a web page and perform the Accessibility Audit. This can be done automatically every time afterNavigatTo() is called. In the following code example, we will inject the axe_testing.js file provided by the Google Accessibility Developer Tools and perform the audit, which will print a report on the console:

public class IAmTheEventListener2 extends AbstractWebDriverEventListener {

    @Override
    public void beforeNavigateTo(String url, WebDriver driver) {
        System.out.println("Before Navigate To "+ url);
    }

    @Override
    public void beforeNavigateBack(WebDriver driver) {
        System.out.println("Before Navigate Back. Right now I'm at "
                + driver.getCurrentUrl());
    }

    @Override
    public void afterNavigateTo(String to, WebDriver driver) {
        try {
            JavascriptExecutor jsExecutor = (JavascriptExecutor) driver;
            URL url = new URL("https://raw.githubusercontent.com/GoogleChrome/" +
                    "accessibility-developer-tools/stable/dist/js/axs_testing.js");
            String script = IOUtils.toString(url.openStream(), StandardCharsets.UTF_8);
            jsExecutor.executeScript(script);
            String report = (String) jsExecutor.executeScript("var results = axs.Audit.run();" +
                    "return axs.Audit.createReport(results);");
            System.out.println("### Accessibility Report for " +  driver.getTitle() + "####");
            System.out.println(report);
            System.out.println("### END ####");

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

The report is printed in the console, as shown here:

### Accessibility Report for Google####
 *** Begin accessibility audit results ***
 An accessibility audit found
 Warnings:
 Warning: AX_FOCUS_01 (These elements are focusable but either invisible or obscured by another element) failed on the following element:
 #hplogo > DIV > .fOwUFe > A
 See https://github.com/GoogleChrome/accessibility-developer-tools/wiki/Audit-Rules#-ax_focus_01--these-elements-are-focusable-but-either-invisible-or-obscured-by-another-element for more information.
Warning: AX_TEXT_02 (Images should have an alt attribute) failed on the following element:
 #hplogo > DIV > .fOwUFe > A > .fJOQGe
 See https://github.com/GoogleChrome/accessibility-developer-tools/wiki/Audit-Rules#-ax_text_02--images-should-have-an-alt-attribute-unless-they-have-an-aria-role-of-presentation for more information.
...
 *** End accessibility audit results ***
 ### END ####

This report contains a collection of audit rules that check for common accessibility problems.