Remove language="JavaScript" from your <script> tag. It's deprecated. One should move forward with web development.
Your <style> tag is defined improperly. You need to add: type="text/css" into it.
Use classes...It'll allow you to put your CSS into one section and repeat it everywhere:
<style type="text/css">
div { padding: 1px;}
div.pokemon { float: left; }
div.pokeNew { float: left; background-color: yellow; }
</style>
Then for each div use one or the other:
<div class="pokemon">
<img src=....><br />
Pika-pika
</div>
<div class="pokeNew">
<img src=..."><br />
New Pika!
</div>
(btw, sorry if they're not pokemons. They just look it to me and I had to find an excuse to use it. :p)
Use HTML Tidy to clean up your code formatting. I'm a stickler with having pretty source code. I'm such a stickler, I even alter my scripts to put in the proper tabbing when the page runs. DIV is a block element, like P, so you should format it like so:
<div class="something">
a bunch of text
more text
crappy stuff
</div>
But, like I said, I'm just a stickler for pretty source.
In reply to:
It looks like the divs with a yellow background go only underneath the other yellow-backgrounded divs.
You're using padding. Cause of this, you'll get an appearant 1 pixel border around the content within each div with a background colour. If you change it to margin, the border will go away.