This brief post is result of a question posted by Icaro Perseo. He used org-mode for blogging using org2blog, but was not satisfied with default HTML tags used by org-mode.

He wanted to change the default emphasis on text when it is converted to HTML in org-mode. By default during conversion from org to HTML,

/text/ converts to <i>text</i>

and

*text* converts to <b>text</b>

He wished to use <em> and <strong> instead of <i> and <b>.

Well, everything can be customized from Emacs and Icaro’s solution to his problem lies in the customization of group org-appearance. To customize this group, type

M-x customize-group org-appearance

and search for the variable Org Emphasis Alist

Variable: Org Emphasis Alist

Now change the value of HTML start tag and HTML end tag to whatever you want.

Update - March 1, 2016: This solution is NOT valid for Emacs-pretest version(25.0.91.1)