Guias HTML para host vazio

When you set href="http://", the browser and the W3C validator attempt to parse this as an absolute URL. According to the URL Standard, a URL with the http or https scheme must include a non-empty host component. The string http:// has the scheme but nothing after the ://, which makes the host empty and the URL invalid.

This issue typically arises when a URL is dynamically generated but the variable or value for the domain is missing, or when a developer uses http:// as a temporary placeholder during development and forgets to replace it.

Why this matters

• Broken navigation: Clicking a link with href="http://" leads to unpredictable behavior. Some browsers may navigate to an error page, while others may interpret it differently.
• Accessibility: Screen readers announce links to users, including their destinations. An invalid URL creates a confusing experience for assistive technology users who expect the link to go somewhere meaningful.
• Standards compliance: The HTML specification requires that href values be valid URLs. An empty host violates the URL parsing rules, causing the W3C validator to flag it as an error.
• SEO: Search engine crawlers may treat invalid URLs as errors, potentially affecting how your site is indexed.

Examples

❌ Invalid: empty host in URL

<a href="http://">Visit our website</a>

This triggers the error because http:// has no host component.

❌ Invalid: same issue with HTTPS

<a href="https://">Secure link</a>

The https scheme also requires a valid host, so this produces the same error.

✅ Fixed: provide a complete URL

<a href="https://example.com">Visit our website</a>

✅ Fixed: use a fragment placeholder if the URL is unknown

If you need a placeholder link during development, use # instead of an incomplete URL:

<a href="#">Visit our website</a>

✅ Fixed: use a relative URL when linking within the same site

<a href="/about">About us</a>

Handling dynamic URLs

If the href value comes from a template or CMS, make sure the variable outputs a complete URL. For example, if a template produces an empty string, you might end up with:

<!-- If {{ site_url }} is empty, this becomes href="http://" -->

<a href="http://{{ site_url }}">Home</a>

Ensure that the variable always resolves to a valid host, or add a fallback so the link is omitted or replaced with a safe default when the value is missing.

The <area> element defines a clickable region within an <map> element, which is used with images to create image maps. When an <area> element includes an href attribute, the browser treats it as a hyperlink. The value of href must be a valid URL, and http:// alone fails validation because the URL specification requires a host after the :// separator. An empty host is not permitted.

This matters for several reasons. Browsers may handle malformed URLs unpredictably — some might ignore the link, others might attempt navigation to a nonsensical destination, and others might throw a network error. Screen readers and other assistive technologies rely on valid href values to announce links correctly and provide meaningful navigation to users. From a standards compliance perspective, the WHATWG URL Standard explicitly rejects URLs with empty hosts, and the W3C validator flags this as an error.

This issue commonly appears when placeholder URLs are left in during development, when CMS tools generate incomplete markup, or when a URL value is dynamically constructed but the host portion ends up empty.

How to fix it

• If the area should link somewhere, replace http:// with the full, intended URL including the host (e.g., https://example.com/page).
• If the area is a temporary placeholder, use href="#" to create a valid no-op link, though be aware this will scroll the page to the top when clicked.
• If the area shouldn’t be interactive, remove the href attribute entirely. Without href, the <area> element is not a hyperlink and won’t be clickable.

Examples

Invalid: empty host in URL

The value http:// has no host, which triggers the validation error.

<img src="diagram.png" alt="Site map" usemap="#siteMap">
<map name="siteMap">
  <area shape="rect" coords="30,23,183,191" href="http://" alt="Home page">
</map>

Fixed: complete URL with a valid host

Providing a full URL with a host resolves the error.

<img src="diagram.png" alt="Site map" usemap="#siteMap">
<map name="siteMap">
  <area shape="rect" coords="30,23,183,191" href="https://example.com/" alt="Home page">
</map>

Fixed: placeholder link with #

If you need the area to remain clickable but don’t have a destination yet, href="#" is a valid placeholder.

<img src="diagram.png" alt="Site map" usemap="#siteMap">
<map name="siteMap">
  <area shape="rect" coords="30,23,183,191" href="#" alt="Home page">
</map>

Fixed: non-interactive area without href

If the area doesn’t need to be a link, simply omit the href attribute.

<img src="diagram.png" alt="Site map" usemap="#siteMap">
<map name="siteMap">
  <area shape="rect" coords="30,23,183,191" alt="Home page">
</map>