If you mean redefine by CSS as in making the H1 tag look in font and color any way you want, then yes.
I waswoundering the same thing, becuase i made a .h1 class and made it how i wanted it to look, and i was woundering if class="h1"> was just as effective as <h1>?
Spacebars appear to be having trouble these days You can style it in a separate CSS file or in the HTML file (but I recommend the external CSS file). You *could* make a p tag look like an h tag, but the value is then lost. You have h tags to define headings. Various software exist that make use of the h tags in a page (such as for creating a table of contents). Use whatever tag makes sense and then style it based on your needs.