I have seen people (including popular digital agencies) using 1 x 1px transparent image, so that they can add page title as alt value.
Does that really increases the value of a web page or that's a spam in search engine's eyes?
Webmasters Stack Exchange is a question and answer site for webmasters. It only takes a minute to sign up.Sign up to join this community
could you show us an example of were you've seen this, i havnt heard it done before as your saying but its seems something that a search engine bot would be able to see quite easily.
What i think it might be is a tracking pixel which is used by sites like quantcast and other ad / analytics providers - for more information on tracking pixels look here - http://support.google.com/dfp_premium/bin/answer.py?hl=en&answer=1347585
I have tested doing this with multiple images repeated in a background and the site is still page one in google after all google penguin updates ,it's better and more safe to use real pictures not blank with repeat alt tags as google will notice there is no image there, try stick to white hat seo