onsubmit="return check() 給form加onsubmit 驗證所有表單後再提交，可以用返回false 來阻止submit提交
<form class="form-horizontal form-signin" role="form" onsubmit="return checksame();"><div class="form-group">
<label class="col-sm-2 control-label">用戶名：</label>
<div class="col-sm-10">
<input type="text" class="form-control" id="" placeholder="用戶名" required=''>
</div>
</div>
<div class="form-group">
<label for="inputPassword3" name="password" class="col-sm-2 control-label">密碼：</label>
<div class="col-sm-10">
<input type="password" class="form-control" id="password" placeholder="請輸入密碼" required=''>
</div>
</div>
<div class="form-group">
<label for="inputPassword3" class="col-sm-2 control-label">密碼：</label>
<div class="col-sm-10">
<input type="password" name="password2" class="form-control" id="password2" placeholder="請再輸入密碼" required=''>
</div>
</div>
<div class="form-group">
<label for="inputEmail3" class="col-sm-2 control-label">Email：</label>
<div class="col-sm-10">
<input type="email" class="form-control" id="" placeholder="[email protected]" required=''>
</div>
</div>
<!-- <div class="form-group">
<div class="col-sm-offset-2 col-sm-10">
<div class="checkbox">
<label>
<input type="checkbox"> 記住登錄狀態
</label>
</div>
</div>
</div> -->
<div class="form-group">
<label for="inputEmail3" class="col-sm-2 control-label">驗證碼：</label>
<div class="col-md-2">
<script type="text/javascript">
function fleshVerifys(){
var time=new Date().getTime();
document.getElementById('verifyImg').src='<{:U('Index/verify')}>&'+time;
}
function checksame(){
var pwd1=document.getElementById("password").value;
var pwd2=document.getElementById("password2").value;
if(pwd1!=pwd2){
alert("兩次輸入的密碼不一致！");
document.getElementById("password").focus;
return false;
}else{
return true;
}
}
</script>
<img id="verifyImg" src="<{:U('Index/verify')}>" onclick="fleshVerifys();" />
</div>
<div class="col-md-8">
<input type="text" class="form-control" id="" placeholder="請輸入驗證碼" required=''>
</div>
</div>
<div class="form-group">
<div class="col-sm-offset-2 col-sm-10">
<input type="submit" class="btn btn-lg btn-success" value='注 冊'/>
</div>
</div>
</form>