function set_text_value_position(obj, spos){
	var tobj = document.getElementById(obj);
	if(spos<0)
			spos = tobj.value.length;
	if(tobj.setSelectionRange){ //兼容火狐,谷歌
			setTimeout(function(){
				tobj.setSelectionRange(spos, spos);
				tobj.focus();}
				,0);
	}else if(tobj.createTextRange){ //兼容IE
			var rng = tobj.createTextRange();
			rng.move(‘character‘, spos);
			rng.select();
	}
}
//调用演示
set_text_value_position(‘login_div‘, -1);  //设置到末尾
set_text_value_position(‘login_div‘, 0); //设置到开头