Does text size and placement on page have an effect on SEO

Question

As Google and other search engines keep trying to get more and more 'human' in terms of understanding what's good and what's spam, is it known if they take into account the size of a heading ie. an thats font size is 40px is going to speak a lot more to the user than a thats font size is 14px?

Similarly, does placement of text factor? E.g. a 300-word article at the bottom of a landing page (not in the footer but below the useful content) would be there just for seo purposes?

I know they look at things like text-indent:-9999px; and white text on a white background, but what about these more border-line practices that both have legitimate uses, but also the possibility to be spammy?

Answer 1

This is similar to the question previously asked here: Is heading (h1, h2, h3...) font size relevant for SEO? but requires it's own answer.

Question #1: Does the font-size (style) affect the SEO value of headings?
Answer: No. Except when used to de-emphasise or obscure the headings in a way that is clearly meant to either manipulate the emphasis, or to hide the text altogether (font-size:0 for example).

Question #2: Does placement factor?
Answer: It depends - if it's there "just for SEO purposes" then you're sailing very close to the danger-line in terms of triggering a flag that Google may take a dim view on. I have worked on a number of different websites where (both normal and absolute) positioning of content has been trialled with no material impact - however, the content was actually there to provide additional information for the human visitors, not just the search bots.

Search engines, Google in particular have sophisticated algorithms based on patents such Page-level template detection using isotonic smoothing and Techniques for approximating the visual layout of a web page, not to mention scouring the billions of web-pages that use different techniques to hide/obscure/inject content, so are very easily able to identify almost every technique used to optimise pages for bots, rather than for humans.