_header.html.erb

<div class="navbar navbar-fixed-top">
    <div class="navbar-inner">
        <div class="container-fluid">
            <a class="brand" href="/">Project name</a>
            <div class="nav-collapse">
                <ul class="nav">
                    <!---easy ver start-->
                    <li <%= request.path == '/' ? 'class="active"' : '' %>><a href="/">Home</a></li>
                    <li <%= request.path == '/about.html' ? 'class="active"' : '' %>><a href="/about.html">About</a></li>
                    <li <%= request.path =~ /^\/products\// ? 'class="active"' : '' %>><a href="/products/index.html">Products</a></li>
                    <li <%= request.path == '/contact.html' ? 'class="active"' : '' %>><a href="/contact.html">Contact</a></li>
                    <!---easy ver end-->
                    <!---RUBY ver start-->
                    <%#= content_tag(:li, link_to('Home', '/'), :class => ("active" if request.path == '/' )) %>
                    <%#= content_tag(:li, link_to('About', '/about.html'), :class => ("active" if request.path == '/about.html' )) %>
                    <%#= content_tag(:li, link_to('Products', '/products/index.html'), :class => ("active" if request.path =~ /^\/products\// )) %>
                    <%#= content_tag(:li, link_to('Contact', '/contact.html'), :class => ("active" if request.path == '/contact.html' )) %>
                    <!---RUBY ver end-->
                </ul>
                <p class="navbar-text pull-right">Request path is <span class="label label-info"><%= request.path %></span></p>
            </div><!--/.nav-collapse -->
        </div>
    </div>
</div>