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I recently added HTML5 <nav> and <footer> elements to a page, thinking that HTML5-capable browsers would use them for semantic things like navigation, while older browsers would see them as user-defined tags and apply CSS styles to them like ordinary <div> elements.

When I was working on this, I remember seeing a warning that a version or some versions of Internet Explorer didn't support user-defined tags, with a link to HTML5shiv as a possible solution. Unfortunately I don't remember where I saw it or which version/versions might be affected (which would indicate how concerned I should be about this problem).

If other common browsers share this problem, it would help to know about those too.

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take a look here html5test.com – Liam Sorsby Feb 11 '14 at 16:50
The title does not match the content. The title says “user-defined”, but the text refers to HTML5 tags. – Jukka K. Korpela Feb 11 '14 at 17:18
See these recent related questions: webmasters.stackexchange.com/questions/57805/… and webmasters.stackexchange.com/questions/57726/…. – dan Feb 11 '14 at 18:47
^^ The HTML5 tags are user-defined tags when there is no HTML5 support. – Wutaz Feb 11 '14 at 21:18
up vote 5 down vote accepted

The Can I Use? website is excellent to determine browser support for various features, including HTML5 semantic tags:


You'll see that IE8 and below let the team down. If you need to support IE6, 7, and 8, then using the HTML5 shiv is a good idea. IE8 is still in use by roughly 7% of visitors, according to StatCounter, but that percentage may be higher for some audiences. It's worth checking your own stats if you have them and making a decision based on that.

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I thought about it and decided that this technically doesn't answer my question, but it's close enough. I can deduce from that page which browsers support user-defined tags because "partial support" is defined as allowing the style to be set manually, strongly implying that styles can be set to any tag that isn't fully supported. – Wutaz Feb 11 '14 at 21:46
caniuse is never up to date, so typically its wrong. the best place to determine browser features and support? the browser's documentation. aka msdn, mdn, opera, apple, and google.dev. – albert Feb 12 '14 at 8:30
@albert The data that backs Can I Use is open source and published on GitHub. It's updated pretty regularly. If you find inaccuracies you can always contribute corrections there. – Nick Feb 13 '14 at 8:37
i'm very well aware. its a great tool...but its not the source, and i've found plenty of inconsistencies. – albert Feb 13 '14 at 8:44

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