Tags
Different browsers, like IE or FireFox, interpret CSS rules differently. In some cases you will have to indicate the height of the lines or the padding or the margins.
For instance with the h1 to p tags, you will notice that the first line will have a slightly different position in IE than with FireFox.
Chapter Navigation:
Solution
Once again there is a simple solution, at the very least indicate in the CSS rule h1,...,p a height of 0 pixel. Making all the margins 0 pixels will also do.
CSS Example
h1, h2, h3, h4, p { margin-top: 0px; }
or
h1, h2, h3, h4 { margin: 0px; }