El error está en otro lado, acabo de probar el código tal como lo tienes y no me ha dado problema alguno:
Código html:
Ver original<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> <meta http-equiv="content-type" content="text/html; charset=utf-8" /> <script language="javascript"> window.onload = function()
{
var lis = document.getElementsByTagName("img");
for (var i=0;i<lis.length;i++) {
lis[i].onmouseover = function()
{
this.src='http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_pos.gif';
};
}
};
<img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br /> <img src="http://static.forosdelweb.com/fdwtheme/images/reputation/reputation_off.gif" alt="" /><br />
Probado en Firefox