function isIns(){

        var i, j;
        var count;
        
        count = 0;
        
        for( i = 0; i < document.xform.wallpaper.length; i ++){
            
            if( document.xform.wallpaper[i].checked){
                
                count ++;
            
                break;
            
            }
                
        }
        
        if( count == 0){
            
            alert('請選擇一款您要轉寄的圖樣！');
            document.xform.wallpaper[0].focus();
            return false;
            
        }        
        
        count = 0;

        if( ! isEmail( document.xform.sendermail.value) || document.xform.sendermail.value.length == 0){
            
            alert('請輸入寄件人信箱！');
            document.xform.sendermail.focus();
            return false;    
                        
        }

        for( i = 0; i < document.xform.receivermail.length; i ++){
        
            if( document.xform.receivermail[i].value.length != 0){

                count ++;

                if( ! isEmail( document.xform.receivermail[i].value)){
                    
                    alert('請輸入寄件人信箱！');
                    document.xform.receivermail[i].focus();
                    return false;    
                                
                }

                if( document.xform.sendermail.value == document.xform.receivermail[i].value){

                    alert('寄件人與收件人信箱不能重覆！');
                    document.xform.receivermail[i].focus();
                    return false;  
                    
                }
                
                for( j = 0; j < document.xform.receivermail.length; j ++){
                    
                    if( document.xform.receivermail[i].value == document.xform.receivermail[j].value && i != j){

                        alert('收件人信箱不能重覆！');
                        document.xform.receivermail[j].focus();
                        return false;
                        
                    }                    
                    
                }            

            }
            
        }

        if( count == 0){
            
            alert('請最少輸入一個收件人信箱！');
            document.xform.receivermail[0].focus();
            return false;
            
        }

        if( ! confirm('在按下確定送出之前，請確認您所輸入的資料是否正確無誤！')){
            
            return false;
        
        }
        
    }