Which is the best way of make text bold?

[soltec]

Is there a difference between , and font-weight: bold, in terms of SEO weighting?

Does font size make a diffence, relative to the average font size of the page?

[RyanKent]

Is there a difference between , and font-weight: bold, in terms of SEO weighting?

****Each search engine is a private company and can choose to weigh things as they see fit. I can share for Google those factors are treated identically. It is likely other search engines treat them the same but I cannot confirm that information.

Does font size make a diffence, relative to the average font size of the page?

The historic best method to adjust font-size was the use of header tags (h1, h2....h6). This method affects font size and is weighted by Google.

If you attempt to manipulate search results by changing font-size (such as font size = 1) then that certainly can impact SEO with a penalty.

Google is definitely aware of relative font-size and it likely is a ranking factor. I have seen numerous indications of such, but am not aware of any 100% conclusive statement to that effect.****