We use something like this [use in one line]:
<a title="send to Facebook"
href="http://www.facebook.com/sharer.php?s=100&pFacebook share button and custom text [closed]=YOUR_TITLE&p[summary]=YOUR_SUMMARY&p[url]=YOUR_URL&p[images][0]=YOUR_IMAGE_TO_SHARE_OBJECT"
target="_blank">
<span>
<img width="14" height="14" src="'icons/fb.gif" alt="Facebook" /> Facebook
</span>
</a>