HTML Checking for Large Sites
Rocket Validator automatically checks your pages on the W3C Validator.
Bad value “mailto: X” for attribute “href” on element “a”: Illegal character in scheme data: space is not allowed.
<a>
tags can be used to link to an email address using the mailto
protocol in the href
attribute. Ensure that there is no space in the email address.
<a href="mailto: liza@example.com">This is wrong as it contains an space</a>
<a href="mailto:liza@example.com">This is OK</a>
Related W3C validator issues
A button
element, or an element with the role=button
attribute, is not allowed to be nested inside an <a>
element.
An <a>
element cannot contain a descendant element with the attribute tabindex
.
Learn more:
The value contact
is not a valid option for the autocomplete
attribute on an <input>
element.
Learn more:
All HTML elements may have the hidden
boolean attribute set. When specified on an element, it indicates that the element is not yet, or is no longer, relevant, so browsers won’t render it.
Boolean attributes don’t accept values, its presence represents the true
value and its absence represents the false
value.
<!-- This is invalid because the hidden attribute should not have a value set -->
<div hidden="false"></div>
<!-- The correct way to hide a div is like this -->
<div hidden>This will be hidden</div>
<!-- And to show the element, we just don't hide it -->
<div>This won't be hidden</div>
Read more:
An <a>
element has been found with an invalid href
attribute, containing more than one #
adjacent character.
The #
is used to separate the fragment part of an URI (typically used to indicate a section within a document). For example, this is a valid link to a URI containing a fragment:
<a href="https://example.com/faqs#pricing">pricing</a>
The next example is invalid because it contains two adjacent #
characters, so that the fragment part would be #pricing
instead of pricing
:
<a href="https://example.com/faqs##pricing">pricing</a>
Learn more:
The href
attribute of an <a>
element contains an invalid character, that should be properly encoded as a URI percent-encoded character.
Learn more:
The href
attribute on the link
element must not be empty.
The src
attribute on an <img>
element contains an invalid character, that should be properly encoded as a URI percent-encoded character.
Learn more:
The target
attribute on <a>
elements can’t be blank.
This attribute defines the browsing context for links, that is, where should the linked documents be opened. This was used extensively on the now deprecated <frame>
element, so you could give the name of the frame to open the document in, but is now more used to force links to open in a separate tab or window using target="_blank"
. Another option is using a name, so the new browsing context can be referred to on subsequent clicks on links with the same target
.
For example, this will force the links to open on a new tab:
<a href="https://example.com" target="_blank">will open a blank tab</a>
Learn more:
The href
attribute on an a
tag expects a valid URL, but only http://
was found.
The href
attribute on an <a>
link contains a space character, which is not allowed. If you’re trying to link to a phone URL, review the href
attribute to remove unallowed characters, as in this example:
<!-- Invalid as it contains a space character -->
<a href="tel: +123456789">call me</a>
<!-- Valid -->
<a href="tel:+123456789">call me</a>
Source:
Space characters are not allowed in href
attributes. Instead, they should be converted to %20
. In this example, the first line is invalid and the second is valid:
<a href="https://example.com#some term">invalid</a>
<a href="https://example.com#some%20term">valid</a>
The href
attribute on an element <a>
contains a character that is not allowed, and should be encoded.
Some typical examples include the pipe character |
that should be replaced by its encoded alternative %7C
, and the left square bracket [
that needs to be encoded as %5B
.
The href
attribute on an <a>
tag contains an space, which is not allowed. Consider replacing space characters with “%20”.
The at symbol (@
) should be percent-encoded as %40
in order to include it at an href
attribute.
The href
attribute on an element <link>
contains a character that is not allowed, and should be encoded.
Some typical examples include the pipe character |
that should be replaced by its encoded alternative %7C
, and the left square bracket [
that needs to be encoded as %5B
.
A <pattern>
element has been found with an invalid ID. Check the format of the ID and ensure it does not start with a digit, full stop (.) or hyphen (-).
The <pattern>
element is used within <svg>
elements, which use XML 1.0 syntax. That syntax specifies that valid IDs only include designated characters (letters, digits, and a few punctuation marks), and do not start with a digit, a full stop (.) character, or a hyphen-minus (-) character.
Learn more:
The media
attribute on a <link>
element has not been recognized.
This attribute specified what media the linked resource is optimized for. As an example, the following will link a general stylesheet, and a specific one for printing:
<head>
<link rel="stylesheet" type="text/css" href="general.css">
<link rel="stylesheet" type="text/css" href="print.css" media="print">
</head>
Valid values for this attribute include:
all
. Default, used for all media.
print
. Used for printers and print previews.
* screen
. Used for computer, tablets or smartphone screens.
Learn more:
The value used in the target
property of an <a>
element has been identified as a keyword because it starts with an underscore _
, but it’s not a valid keyword.
Values starting with an underscore for the target
property are used for reserved keywords like _blank
, _self
, _parent
or _top
.
Learn more:
The value provided on the type
attribute of an a
element is not a valid MIME type.
The type
attribute expects a MIME type that hints at the linked URL’s format.
Read more:
The type
attribute on <a>
elements, when present, gives a hint on the MIME type of the linked resource, for example:
<a href="application/pdf" src="book.pdf">Read our book</a>
<a href="image/jpeg" src="photo.jpeg">See a photo</a>
That is, we’re talking about the type of the linked resource, not the type of the <a>
element, as it’s sometimes misunderstood. The following example is invalid because button
is not a valid MIME type.
<a href="/order.php" type="button">Submit</a>
Learn more:
The value used to define the type
of a link
is not valid. You’re probably using a URL instead of a valid type.
Example of a valid type
:
<link rel="icon" type="image/png" href="favicon.png">
Read more:
The <a>
element requires either a href
attribute, or a role
attribute.
Learn more:
An </a>
end tag has been found to violate nesting rules. <a>
tags can’t include other <a>
tags inside. Most probable cause is an unclosed <a>
tag, like in this example:
<a href="one.html">Page 1
<a href="two.html">Page 2</a>
Attributes in HTML elements need to be separated by space, in this example the first line is invalid and the second one is valid:
<a href="page.php"class="big">link</a>
<a href="page.php" class="big">link</a>
An <a>
tag can’t include other <a>
tags inside. Most probable cause is an unclosed <a>
tag, like in this example:
<a href="one.html">Page 1
<a href="two.html">Page 2</a>
An <a>
element has been found in an invalid place within a <table>
element.
For example, the following code would cause this issue:
<table>
<tr>
<a href="#">link</a>
</tr>
</table>
Instead, the <a>
element should be inside a <td>
element, as a <tr>
can’t hold content directly:
<table>
<tr>
<td>
<a href="#">link</a>
</td>
</tr>
</table>
A button
element, or an element with the role=button
attribute, is not allowed to be nested inside an <a>
element.
A <label>
tag can’t be used inside an <a>
tag. Consider using other tags like <span>
.
Links created with the <a>
element no longer accept a shape
attribute. In order to define image maps, use the <area>
element instead.
Learn more:
50,000 Accessibility and HTML checks per month. Fully automated.
Let our automated scanner check your large sites using Axe Core and W3C Validator.