function form_check(form_name)
{
		//check null
		for(i=0;i<form_name.length;i++)
  	{
     		form_name.elements[i].value=form_name.elements[i].value.replace(/^\s+|\s+$/g, "");
     		if(form_name.elements[i].getAttribute("checknull"))
     		{
     				if(form_name.elements[i].value=='')
     				{
     					alert(form_name.elements[i].getAttribute("msg")+'不得為空白');
     					form_name.elements[i].focus();
     					return false;
     				}	
     		} 
    }
    
    //check length
    for(i=0;i<form_name.length;i++)
  	{
				if(form_name.elements[i].getAttribute("minlength"))
				{
						if(form_name.elements[i].value.length< form_name.elements[i].getAttribute("minlength") || form_name.elements[i].length > form_name.elements[i].getAttribute("maxlength"))
						{
								alert(form_name.elements[i].getAttribute("msg")+'長度需介於' + form_name.elements[i].getAttribute("minlength") +'~'+ form_name.elements[i].getAttribute("maxlength"));	
								form_name.elements[i].focus();
     						return false;
						}
				}
    }
    
    //check type
    
    //1 u_id
    re=/\w/;
    if (!re.test(form_name.u_id.value)) 
    {
    		alert("帳號格式只允許 a~z A~Z 0~9 _的字元"); 
    		return false;
    }
    
   	//2 pass format
    if(form_name.u_pass.value)
    {
    		for(k=0;k<form_name.u_pass.value.length;k++)
    		{
    				if(escape(form_name.u_pass.value.charAt(k)).length>1)
    				{
    						alert("密碼請用單一字元，不支援全型字、中文字");
    						return false;			
    				}
     				
     		}
    }
}