I have the following HTML code:
...
To get the same size on both browser you have to set the same initial values to all the CSS elements, like a reset.
This is how I fixed the problem: put this at the beginning of your css file
body, div, dl, dt, dd, ul, ol, li, h1, h2, h3, h4, h5, h6, pre, code, form, fieldset, legend, input, button, textarea, p, blockquote, th, td, a
{
margin-top: 0px;
margin-right: 0px;
margin-bottom: 0px;
margin-left: 0px;
padding-top: 0px;
padding-right: 0px;
padding-bottom: 0px;
padding-left: 0px;
border-top-width: 0px;
border-right-width-value: 0px;
border-bottom-width: 0px;
border-left-width-value: 0px;
}
Now you have to fix some aspect changes on your page but it will look almost the same on all the browsers.