Found an interesting and very active thread today on HighRankings detailing some tests by several members about the importance placed on bold and H1 attributes in the code. I haven't seen these certain SEO tests discussed in a while so its been interesting following the discussion that is taking place. There are invariably some disagreements about the importance of these attributes and the While many of the tests conducted are not conclusive in any way, some members raise some good points about how search engines programming algorithms assign relevance to rankings of a website. One of the members who started the thread conducted a simple test under the phrase "kkhiazna" using "h1, b, big + b, big, h2, font size +1, and font size 2 + b.
Another member paisley, posts some interesting comments about how these attributes get scored:
"it's based on content relevance. Does the h1 describe the text that follows after the h1>. Italics is a 2 score and bold is a 3 score.. fyi. H1s should be a 5 score unless the words used in the H1 are not repeated in the following text, then it is a 3 score (same as bold)."
Then as I was reading the post some disputes started to erupt, Jill did not agree with the assessment placed by the member paisley. He did not like her response. Posts got deleted by members and admin. She then responds about b and h1 tags.
And I'm not saying that H tags do or do not help. I've just not seen any recent evidence to conclude anything either way. Therefore, I would suggest that you use those tags where they make sense to do so, as per WC3 specifications, and not really worry about it as far as SEO is concerned.
As to the weight any given tag is given, one cannot place a number on it, because each tag doesn't work in isolation, but in a synergistic way with the other tags, copy, links, etc. on any given page.
Other members have some opinions and conclusions about the importance of these attributes. Murugan says that "Both are important and should be applied whenever necessary. I have seen some sites without H1 are ranking well. Most of the times we test only 1 r 2 factors, but SE's rank the sites with 100+ factors.". Good point.
From my own experience I use h1, h2, and h3 in my seo as more of a way to hierarchal arrangement of a page, the rule is that what’s in the headers must also be in the content, as keywords are of prime importance for the benefit of the h1, h2, and h3 tags. Bolds and Italics are just as important but to be used sparingly as needed for the benefit of the user and the search engine. Tie that in with other work being done on the page, and it works well for ranking.
Read the heated discussion at Highrankings