This is my html code
Code:
<html>
<head>
<title>XXX company</title>
<link rel='stylesheet' media="screen" type='text/css' href='style.css' />
</head>
<body>
<div id="container">
<div id="header">
<div id="logo">
  <h1>XXX company</h1>
</div>

<div id="menu_bar">
<ul>
  <li><a href="#"><img src="img/but_home.jpg"></a></li>
  <li><a href="#"><img src="img/but_company.jpg"></a></li>
  <li><a href="#"><img src="img/but_service.jpg"></a></li>
  <li><a href="#"><img src="img/but_calculation.jpg"></a></li>
  <li><a href="#"><img src="img/but_news.jpg"></a></li>
  <li><a href="#"><img src="img/but_message.jpg"></a></li>
  <li><a href="#"><img src="img/but_partner.jpg"></a></li>
  <li><a href="#"><img src="img/but_contact.jpg"></a></li>
</ul></div>

/div>
</body>
</html>
This is the style.css
Code:
body {
  text-align:center;
}

div {
  margin:0;
  padding:0;
  outline:1px solid red;
}
#header {
  height:174px;
  padding:0px;
 
  
}

#logo {
  height:140px;
  background:url(img/top.jpg) no-repeat;
}
.spacer {
clear:left;
}
#menu_bar {
  
  float:left;
  height:34px;
  padding:0px;
  margin:0px;
  text-align:left;
}

li img {
  border:0px;
  margin:0px;
  padding:0px;
}
#lang_bar {
  float:left;
  text-align:left;
}

#menu_bar ul {
  list-style:none;
  margin:0px;
  padding:0px;
}
#menu_bar li {
  display:inline;
  margin:0px;
  padding:0px;
}
#menu_bar li a:link, #menu_bar li a:visited {
text-decoration:none;
font-weight:bold;
}

#lang_bar ul {
  list-style:none;
  margin:0px;
  padding:0px;
}

#lang_bar li {
  display:inline;
  margin:0px;
  padding:0px;
}

#content {
  float:right;
  width:711px;
  text-align:left;
}

#left_col {
  float:right;
  width:291px;
  height:400px;
  background:url(img/left_col.jpg) no-repeat;
  text-align:left;
}

#address {
text-align:left;
}
#container {
  width:1024px;
  margin:20px auto;
}
#footer {
  clear:both;
  height:56px;
  background:url(img/footer.jpg) no-repeat;
  text-align:left;
}
The result is there is a gap between each button image as show below


I have set all stuffs related to element spacing and positioning like margin , padding to zero px.