Stripping simple HTML from posts makes me melancholy

I want WP2.1 to stop breaking simple <div id="myDiv"> tags and the like, that I hand-enter as I type in Posts.

I have dragged through previous support on this and cannot find a simple answer to my simple question.

I want to write posts with a few, ‘simple’ HTML tags of my own dropped in.

Example: I have 6 paragraphs of text, I want three columns on the main body of the page page, each with two paragraphs. Answer: I simply wrap, in code view editor, the pairs of para’s in div’s that have unique IDs and target them from style.css. This works a treat. Smiles all round. The problem comes if I make any edits (in rich-text OR code editor). When I do this:

<div id="col1">Hello Dolly, it's nice here...</div>

…becomes this…

<p id="col1"> </p>Hello Dolly, it's nice here...</div>

I have tried asking WP not to correct XHTML and researched plugins. However, I was hoping to avoid plugins if I could, just looking for the cleanest/simplest setup.

I am using WP 2.1. I will use a recommended plugin if it’s designed to play nicely with 2.1.

I might perhaps make page templates(?) but I am not sure this will be flexible enough for me and it also sounds like a pretty brutal solution to surely a fairly big question – can I add valid, simple, additional tags to my Posts and know they will be respected? If I could add or could add some (a listed sub-set) it would empower those of us who want to use WP more for publishing.

Grateful for any response. Thanks in advance,

-Alan