在这个input输入框中按enter进行提交表单
<form onsubmit="if(event.srcElement.name=='bb'){this.submit()}else{return false}">
<input name=a size=20>
<input type=button name=bb onclick="submit();">
</form>
<input name=a size=20>
<input type=button name=bb onclick="submit();">
</form>
