帮忙看看这段JS在火狐下为什么不能用,怎么改，才能兼容火狐
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>无标题文档</title><script type="text/javascript" language="javascript">function FunCheckCosts() { //不为空的文本框的ＩＤ if (!CheckFields("name,pwd")) { alert("信息必须填写完整!"); return false; }}function CheckFields(txtChecks){ var oArray = txtChecks.split(","); for (var i=0;i<oArray.length;i++) { if (document.getElementById(oArray[i]).value.replace(/\s/g,"") == "") { try { document.getElementById(oArray[i]).focus(); } catch (e) {} event.returnValue = false; return false; } } return true;}</script></head><body><form action="" method="post" onsubmit="return FunCheckCosts()"><input type="text" name="name" id="name" /><input type="text" name="pwd" id="pwd" /><input type="submit" name="button" value="提交" /></form></body></html>