提交后保留输入框内容问题

<head>
<script language="JavaScript">
function subcheckstock()
{
if (stocksearch.partsearchnum.value.length==0 || stocksearch.partsearchnum.value.length<1 )
{
alert("输入数据太短了！);
stocksearch.partsearchnum.focus();
return false;
}
stocksearch.submit()
}
</Script>
</head>
...
<form action="stock.asp?isreread=Y&issearch=Y"" method="post" name="stocksearch">
<input type="text" name="partsearchnum" id="partsearchnum2" value=<%=request("partsearchnum")%> >　
<img src="img/GObutton.gif" width="21" height="21" border="0" onclick=subcheckstock() style="cursor:hand">
</form>

...

<iframe name="frame" id="ifrmbaby0" width="750" height="155" frameborder="0" scrolling="no" onload="this.height=this.Document.body.scrollHeight" marginwidth="1" marginheight="1" align="top" src ="stockdisp.asp?isreread=Y&issearch=Y&partsearchnum=<%=disppartsearchnum%>&searchsele=<%=dispsearchsele%>" ></iframe>
...

问题：当在Form中的partsearchnum输入框输入查询内容，如ABC*DEF后，执行submit后，partsearchnum输入框的内容还是显示ABC*DEF，但是如果输入ABC DEF，则partsearchnum输入框的内容还是显示ABC，空格后面的都不显示了，请问这是什么原因？