1 pixels is the minimum border width for webdesign (due to the definition of the word pixel).
But the way you're applying styles is not using pixels. Try this CSS instead:
Code:
<table cellpadding="4" cellspacing="0" style="width: 600px; height: 400px; height="400"; border: solid 1px #003399;">
Try that to see if it achieves the affect you are wanting.
Also, especially with such a great tool as Dreamweaver, you should look into learning CSS more fully, as well as using divs for formatting (instead of tables). Best of luck!