W3C mobileOK Checker

The label of each of the following failure messages contains its severity, its category, and a short description of the failure completed by the underlying best practice that triggered the failure.

1. Severity: ; category: ; description: More than 25% of the page characters are extraneous (whitespaces or comments) ; Best Practice: MINIMIZE

   Why?

   Given the limitations of mobile networks, sending extraneous whitespaces and comments make pages slower and more costly to load.

   How?

   Remove useless whitespaces and comments by adding a cleaning step in the publication process (e.g. through tidy).

   Where?

   Triggered by the resource under test.

   More information

   Severity: medium

   A mobile constraint has not been taken into account or the page relies on implicit hypotheses that could turn out to be wrong. For instance, a more conservative use of the network is possible (e.g. whitespaces account for more than 10% of the size of the page) or the character encoding is not explicitly set in the page.

   Category: Keep it small

   Smaller sites make users happier by costing less in time and money.

   Best practice: MINIMIZE

   Use terse, efficient markup.

   Top

2. Severity: ; category: ; description: The document does not validate against XHTML Basic 1.1 or MP 1.2. ; Best Practice: VALID MARKUP

   Why?

   The document is invalid XHTML or uses elements or structures that are not allowed in the XHTML Basic 1.1 specification. This is likely to be problematic for mobile browsers who are more sensitive to the structure of the content than desktop browsers.

   How?

   Check the page with the W3C Markup Validator
   While unknown elements are likely to be ignored by browsers, a simple syntax error may invalidate the document to the point where browsers cannot render it anymore. Also bear in mind that checks were run against a tidied version of the document. The tidying process may have modified the structure and semantics of the original document and may have either created new problems or fixed existing ones.

   Where?

   Triggered 4 times by the resource under test:

   • Line 6, Column 62 — Attribute "class" is not allowed for element type "html".
   • Line 25, Column 117 — Attribute "sizes" is not allowed for element type "link".
   • Line 68, Column 10 — The content of element type "script" must match "null".
   • Line 87, Column 7 — The element type "link" must be terminated by the matching end-tag "</link>".

   More information

   Severity: low

   Useful improvements are possible.

   Category: Rely on Web standards

   In the highly fragmented market of devices and browsers, standards are the best guarantee for interoperability.

   Best practice: VALID_MARKUP

   Create documents that validate to published formal grammars.

   Top

3. Severity: ; category: ; description: The embedded image or object is not of type image/gif or image/jpeg (image/png) ; Best Practice: CONTENT FORMAT SUPPORT

   Why?

   The document contains images that are not in GIF or JPEG format, or are not correctly served by the Web server. Images in formats other than GIF or JPEG may not work on some mobile browsers.

   How?

   • Convert with an image editor the said images either to GIF or to JPEG, depending on the type of images;
   • Either update the links to these new versions, or use Content Negotiation to have both versions available and served depending on the browser capabilities.

   Where?

   Triggered by http://www.cebit2go.de/cebit13/upload/1360848510636_cebit_poland_smartphonebanner.png.

   More information

   Severity: low

   Useful improvements are possible.

   Category: Rely on Web standards

   In the highly fragmented market of devices and browsers, standards are the best guarantee for interoperability.

   Best practice: CONTENT_FORMAT_SUPPORT

   Send content in a format that is known to be supported by the device.

   Top

4. Severity: ; category: ; description: Either the height or width attribute is missing ; Best Practice: IMAGES SPECIFY SIZE

   Why?

   When the width and height attributes are not specified on an image, browsers need to reflow the page when the image has finished loading, which may disrupt the user experience.

   How?

   Add width and height attributes matching the actual dimensions of the image.

   Where?

   Triggered by the resource under test:

   • Line 157
     … <img src="/cebit13/upload/1360848510636_cebit_poland_smartphonebanner.png" />

     The Checker could not determine the dimensions of the image. Consider using the following code where XX and YY should match the actual width and height of the image:

     <img width="XX" height="YY" src="/cebit13/upload/1360848510636_cebit_poland_smartphonebanner.png" />

   More information

   Severity: low

   Useful improvements are possible.

   Category: Check graphics and colors

   Images, colors, and style brighten content, but require care: devices may have low-contrast screens or may not support some formats.

   Best practice: IMAGES_SPECIFY_SIZE

   Specify the size of images in markup, if they have an intrinsic size.

   Top

5. Severity: ; category: ; description: The alt attribute is missing ; Best Practice: NON-TEXT ALTERNATIVES

   Why?

   On top of the Web Content Accessibility Guidelines reasons to recommend the definition of the alt attribute on images, there are a number of reasons why images may not be displayed on mobile devices: the image is too big, the intermittent connection prevented the browser from downloading the image, the user deactivated the rendering of images to save time (and possibly money), ... In such cases, the alternative text will be displayed to help the user understand the missing image(s).

   How?

   Define an alt attribute to all the images of the page. Note that if the images are simply decorative, an empty alt attribute is appropriate.

   Where?

   Triggered by the resource under test:

   • Line 157
     … <img src="/cebit13/upload/1360848510636_cebit_poland_smartphonebanner.png" />

   More information

   Severity: low

   Useful improvements are possible.

   Category: Check graphics and colors

   Images, colors, and style brighten content, but require care: devices may have low-contrast screens or may not support some formats.

   Best practice: NON-TEXT_ALTERNATIVES

   Provide a text equivalent for every non-text element.

   Top

6. Severity: ; category: ; description: The total size of the page (26.7KB) exceeds 20 kilobytes (Primary document: 9.2KB, Images: 17.1KB, Style sheets: 0, Redirects: 399B) ; Best Practice: PAGE SIZE LIMIT

   Why?

   Big pages require a possibly high cost and a long waiting time in many mobile networks. For instance, on many mobile networks, downloading 100KB worth of data takes as long as 1 minute.

   How?

   Focus on the piece of information that you want to deliver. Scale down images to a reasonable size. Remove images that are not essential to the layout of the page. Make sure to separate CSS styles defined for screen and handheld media types so that only relevant CSS styles are downloaded by most devices.

   Where?

   Triggered by the resource under test.

   More information

   Severity: low

   Useful improvements are possible.

   Category: Keep it small

   Smaller sites make users happier by costing less in time and money.

   Best practice: PAGE_SIZE_LIMIT

   Ensure that the overall size of page is appropriate to the memory limitations of the device.

   Top

7. Severity: ; category: ; description: The document uses scripting ; Best Practice: OBJECTS OR SCRIPT

   Why?

   Scripting can be used, but shouldn't be relied upon, since many mobile devices do not support or hardly support scripting. The page should still be usable when scripting is not enabled.

   How?

   Use scripting to enhance your page, but degrade gracefully when scripting is not supported.

   Where?

   Triggered 10 times by the resource under test:

   • Line 32
     … <script src="/cebit13/static/1vXORVkZK58St3QjdbzerXZDi9MfZQ8Q3wCyumiNiep.js" type="text/javascript" />
   • Line 37
     … <script type="text/javascript"> contextMenuUrl
   • Line 62
     … <script type="text/javascript"> $(function() {
   • Line 72
     … <script src="/cebit13/static/4TqToE88WvgVhJlbb8ELccVRIZVrwqcaPpOaByYae4B.js" type="text/javascript" />
   • Line 75
     … <script src="/cebit13/static/UsD9Hzq7EVLcedoEijpLWgyPjMy7HBvuQz6OZLMlMe0.js" type="text/javascript" />
   • Line 82
     … <script src="/cebit13/static/jSKoK8QV01qzn7oIyuse0eSV8cOji6TqsPYgDsaIJpu.js" type="text/javascript" />
   • Line 85
     … <script src="/cebit13/static/MUKO3jBQuMvvirjG77ECQpgiinzR3fQxqyNfV5crqfR.js" type="text/javascript" />
   • Line 86
     … <script src="/cebit13/static/CJ0zyS04D5ZcGuK2Y9QnT1q2CFycZS6OSg50eqmfW5b.js" type="text/javascript" />
   • Line 92
     … <script type="text/javascript"> sponsorings =
   • Line 230
     … <script type="text/javascript"> newsUrl =

   More information

   Severity: informational

   An informational message is a lightweight warning that alerts authors on a point that may have an impact on the user experience on mobile devices if it is not handled with care. For instance, using scripting is not discouraged but authors should check that the page remains usable without scripting. Informational messages do not affect the score of the page.

   Category: Be cautious of device limitations

   When choosing to use a particular Web technology, consider that mobile devices vary greatly in capability.

   Best practice: OBJECTS_OR_SCRIPT

   Do not rely on embedded objects or script.

   Top

8. Severity: ; category: ; description: "Cache-Control" HTTP header is present and contains value "no-cache", or contains value "max-age=0" ; Best Practice: CACHING

   Why?

   A no-cache (or max-age=0) directive prevents browsers from caching the content, and thus requires them to retrieve it through the network every time.

   How?

   If the resource needs to be revalidated each time it is queried, consider using the Last-Modified and/or ETag HTTP headers to limit the complete retrieval of the resource to the cases where the resource has changed. See Mark Nottingham's tutorial on caching to learn more about these techniques.

   Where?

   Triggered 3 times by the resource under test.

   More information

   Severity: warning

   A warning alerts authors on a point that may have an impact on the user experience on mobile devices and that may be worth checking. A warning does not necessarily mean that something needs to be fixed in the page. Warnings do not affect the score of the page.

   Category: Use the network sparingly

   Web protocol features can help improve the user experience by reducing the impact of network bottlenecks and latencies.

   Best practice: CACHING

   Provide caching information in HTTP responses.

   Top

9. Severity: ; category: ; description: A matching HTTP response header does not exist for the meta http-equiv element ; Best Practice:

   Why?

   The mobile HTTP delivery chains usually involve more intermediaries than typical desktop chains (e.g. mobile operator gateways). The intermediaries will stick to the HTTP level, and won't dig in the content of the page to check for meta http-equiv elements. For the value not to be ignored, a matching HTTP header should be defined in the HTTP response.

   Where?

   Triggered 2 times by the resource under test:

   • http-equiv=pragma
   • http-equiv=x-ua-compatible

   More information

   Severity: warning

   A warning alerts authors on a point that may have an impact on the user experience on mobile devices and that may be worth checking. A warning does not necessarily mean that something needs to be fixed in the page. Warnings do not affect the score of the page.

   Category: Use the network sparingly

   Web protocol features can help improve the user experience by reducing the impact of network bottlenecks and latencies.

   Top

10. Severity: ; category: ; description: An HTTP response header that matches the meta http-equiv element exists but their values differ ; Best Practice:

    Why?

    The value of an HTTP response header conflicts with the value of the matching meta http-equiv element defined in the content of the page.

    Where?

    Triggered by the resource under test:

    • HTTP header cache-control

    More information

    Severity: warning

    A warning alerts authors on a point that may have an impact on the user experience on mobile devices and that may be worth checking. A warning does not necessarily mean that something needs to be fixed in the page. Warnings do not affect the score of the page.

    Category: Use the network sparingly

    Web protocol features can help improve the user experience by reducing the impact of network bottlenecks and latencies.

    Top

11. Severity: ; category: ; description: The document is not served as "application/xhtml+xml" ; Best Practice: CONTENT FORMAT SUPPORT

    Why?

    The recommended media type for serving XHTML is application/xhtml+xml. More browsers are likely to support that media type, and optimize the rendering for it. application/vnd.wap.xhtml+xml is widely used and supported in mobile networks as well but is unlikely to be supported by non-mobile browsers.

    How?

    See how to properly configure server mime types. If the page under test uses a non-XML version of HTML, you should first consider switching to XHTML. In any case, do not serve a non-XML version of HTML with an application/xhtml+xml media type.
    Beware: some browsers have no support for application/xhtml+xml (e.g. Internet Explorer) and prompt users to download pages served as such. You should not serve XHTML content to browsers that do not support it. Use Content Negotiation to match the browser's capabilities. See the XHTML Media Types - Second Edition W3C note for more information and in particular the Compatibility Guidelines to follow to have XHTML documents rendered on both XHTML-aware and HTML-only user agents.

    Where?

    Triggered by the resource under test:

    • served as text/html

    More information

    Severity: informational

    An informational message is a lightweight warning that alerts authors on a point that may have an impact on the user experience on mobile devices if it is not handled with care. For instance, using scripting is not discouraged but authors should check that the page remains usable without scripting. Informational messages do not affect the score of the page.

    Category: Rely on Web standards

    In the highly fragmented market of devices and browsers, standards are the best guarantee for interoperability.

    Best practice: CONTENT_FORMAT_SUPPORT

    Send content in a format that is known to be supported by the device.

    Top

12. Severity: ; category: ; description: The document uses a non-XML doctype (no DTD found or doctype declaration invalid) ; Best Practice: CONTENT FORMAT SUPPORT

    Why?

    The document uses a doctype that is not recognized as an XHTML doctype. Mobile browsers can optimize the parsing and rendering of pages with an XHTML doctype.

    How?

    Switch to XHTML if you are using a non-XML version of HTML; or pick a well-known XHTML doctype otherwise.

    Where?

    Triggered by the resource under test.

    More information

    Severity: warning

    A warning alerts authors on a point that may have an impact on the user experience on mobile devices and that may be worth checking. A warning does not necessarily mean that something needs to be fixed in the page. Warnings do not affect the score of the page.

    Category: Rely on Web standards

    In the highly fragmented market of devices and browsers, standards are the best guarantee for interoperability.

    Best practice: CONTENT_FORMAT_SUPPORT

    Send content in a format that is known to be supported by the device.

    Top