au passage, tu fais :
document.getElementById('textemachin').value = document.getElementById('textemachin').value + ':)';
tu peux utiliser à la place l'opérateur +=
document.getElementById('textemachin').value += ':)';
http://www.w3.org/TR/xhtml1/#h-4.10
HTML 4 defined the name attribute for the elements a, applet, form, frame, iframe, img, and map. HTML 4 also introduced the id attribute. Both of these attributes are designed to be used as fragment identifiers.
[...]
Note that in XHTML 1.0, the name attribute of these elements is formally deprecated, and will be removed in a subsequent version of XHTML.
puis plus loin dans C.8. Fragment Identifiers :
Finally, note that XHTML 1.0 has deprecated the name attribute of the a, applet, form, frame, iframe, img, and map elements, and it will be removed from XHTML in subsequent versions.