In both the preview and rendered question, this does not work:

<img src="http://i.stack.imgur.com/R7QBb.jpg" width="100px" height="100px">

..as the image doesn't appear (cleaned up by HTML sanitiser presumably):

It should be here → ← (click the edit button to see the source)

However, strangely omitting the px unit works:

<img src="http://i.stack.imgur.com/R7QBb.jpg" width="100" height="100">

..for example:

Here →

  • (..image was from this related post) – dbr Mar 13 '14 at 11:56
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    According to W3C, height and width are supposed to contain non-negative integers. – Antony Mar 13 '14 at 11:56
  • @Antony Ohh, that explains it! For no justifable reason I thought the img width/height would accept things like 50% and so on - but that would explain it – dbr Mar 13 '14 at 11:58
  • The W3C validator also confirms what @Antony says: Bad value 100px for attribute width on element img: Expected a digit but saw p instead. Note that it is valid HTML 4, it's just invalid HTML 5. – Stijn Mar 13 '14 at 11:58
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    @dbr only CSS accepts units, not HTML attributes. :) – Shadow Wizard Wearing Mask Mar 13 '14 at 12:00
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    From the linked faq: width="" (up to 999; do not include the 'px' extension) – Shadow Wizard Wearing Mask Mar 13 '14 at 12:02