AS we know post titles are indexed and crawled by search engine,. robots.
In SEO the post title is referred as the KING whiles post content is referred as the QUEEN. So if the king is treated with H3 tag instead of H2 tag then I guess you must re-plan your Traffic campaign.
- Go To Blogger> Design > Edit HTML
- Backup your template
- Search for .post h3
- and replace it with .post h2 (keep replacing that for all occurrences of .post h2)
- Then search for,
<h3><data:title/></h3>
and replace it with this,
<h2><data:title/></h2>
Save your template and Done..