[uf-new] img alt content statistics

Manu Sporny msporny at digitalbazaar.com
Sat Jul 14 12:36:02 PDT 2007

Andy Mabbett wrote:
> In message <4698F9F1.1060409 at digitalbazaar.com>, Manu Sporny
> <msporny at digitalbazaar.com> writes
>> The percentages below are the percentages of img tags that contained
>> non-empty attributes:
>> src:    99%
>> height: 66%
>> width:  66%
>> alt:    41%
>> title:   5%
>> id:      4%
>> In general, only 41% of 'img' tags list non-empty 'alt' attributes. In
>> other words - most websites are not using 'alt' attributes for 'img'
>> tags.
> That's a bogus conclusion - empty "alt" attributes are perfectly valid,
> and are appropriate in many cases; and you're counting tags but making
> conclusions about "most websites".

I agree with you, Andy... it seems my statement wasn't clear. Perhaps it
should have read:

"In other words - most websites are using empty 'alt' attributes."


"59% of most websites are complying with the HTML 4.01 specification
regarding usage of 'alt' with image tags."

I used the terminology "most websites" because the data gathered is,
statistically speaking, overkill. Assuming 125,626,329 websites (per
Netcraft) we would need a sample set of 384 websites to get a 95%
confidence level with an interval of 5%.

So, we needed 384 samples - we got 224,671 across 14,077 websites.

If you want to sift through the data yourself, I'll have it up tomorrow.
I'll also be providing all of the source code to crawl, index and
analyze the data.

-- manu

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