Although Word has a built-in “Export to HTML” feature, it has a host of problems that produce less than ideal markup for your website. For one, it is extremely verbose and secondly it has specific problems exporting unicode characters correctly.
As an alternative, you can use this online tool, which outputs nice clean HTML for you to use in your markup. It even has a host of options, including removing empty paragraphs, converting <b> to <strong>, <i> to <em>, replace non-ascii with HTML entities, and replacing smart quotes with ascii equivalents. Very useful.