The alignment of the semantic-ui menu?


I am developing a website using semantic. I want to place my menu bar at Top of the website. I tried the below code. But it is not placing my Menu bar at the top. I see some space on top as well left side. I don't want this. Any one help me to fix this issue??

<!DOCTYPE html>
<html lang="en">
<meta charset="UTF-8">
<title>php userlogin tutorial</title>
<link rel="stylesheet" href="css/semantic.min.css">
<link rel="stylesheet" href="css/tab.min.css">
<script src="js/jquery.js"></script>
<script src="js/semantic.min.js"></script>
<script src="js/tab.min.js"></script>
<nav class="ui menu">
    <a class="active green item">
        <i class="home icon"></i>Home
    <a class="red item">
        <i class="user icon"></i> About us
    <a class="blue item">
        <i class="photo icon"></i> Gallery

Add some custom CSS for that:

.menu-top {
    position: fixed;
    top: 0;
    right: 0;
    left: 0;

And use the class in HTML:

<nav class="ui menu menu-top">