回车网页文本框就提交表单

function checkFloat(event)
{
var e=event||window.event;
var nc = e.keyCode||e.which;
if(nc==13){
valcheck();
}
else if ((nc >= 48 && nc <= 57) || nc == 45 || 40 == nc || 41 == nc || 35 == nc || nc == 46){

}
else
{
event.keyCode = 0;
return ;
}
}
<TR height=17 >
<TD width=60>
<font size=2>验证码：</font>
</TD>
<TD>
<input name="rand" type="text" style="width:120;font-size=12;border=1px solid #7F9DB9;font-family:Arial;background-color:rgb(255,255,255);ime-mode:disabled;" value="1" id="rand" maxlength="15" onkeypress="checkFloat(event);"
ondragenter="return false" onbeforepaste="clipboardData.setData('text',clipboardData.getData('text').replace(/[^/d]/g,''))" >

</TD>
<TD><img src="vImage?u=<%=random.nextInt(1000)%>" border=0></TD>
</TR>