<h1> or <th> better for SEO?

I’m working on some pages and found a table with several <th> tags (which are table header tags used for tables) and wanted to find out if these are beneficial for SEO. I know the the <h1>, <h2>, etc. tags are good for SEO. My plan is to replace the <th> with <h2> or <h3> because I know spiders put those into consideration for SEO for sure. Have anyone you looked into <th> and the possible effects on SEO? Thanks!

web-based design or pc software


I want to revamp (i.e. get rid of "beautiful" flash) a website.

I do not know HTML well (yes, I need to learn). What I DO know is that I want no flash and as little JavaScript as possible. I have a dream of ranking a webpage well in Google and I want a super-clean HTML, fast-loading website.

I want control of position of elements. There are online web creation hosted solutions and PC-installable software that allow this: dragging items to the exact desired location, re-size, etc.

What –for lack of a better word– technology is this? Is it pure HTML?
Does this kind of feature bloat the HTML code to where loading time suffers?

Thank you,