diff --git a/app/controllers/application.rb b/app/controllers/application.rb
--- a/app/controllers/application.rb
+++ b/app/controllers/application.rb
@@ -5,6 +5,18 @@
   # Pick a unique cookie name to distinguish our session data from others'
   session :session_key => '_grader_session_id'
 
+  SINGLE_USER_MODE_CONF_KEY = 'system.single_user_mode'
+
+  def authorization_by_roles(allowed_roles)
+    return false unless authenticate
+    user = User.find(session[:user_id])
+    unless user.roles.detect { |role| allowed_roles.member?(role.name) }
+      flash[:notice] = 'You are not authorized to view the page you requested'
+      redirect_to :controller => 'main', :action => 'login'
+      return false
+    end
+  end
+
   protected
   def authenticate
     unless session[:user_id]
@@ -13,7 +25,7 @@
     end
 
     # check if run in single user mode
-    if defined?(SINGLE_USER_MODE) and (SINGLE_USER_MODE)
+    if (Configuration[SINGLE_USER_MODE_CONF_KEY])
       user = User.find(session[:user_id])
       if user==nil or user.login != 'root'
         redirect_to :controller => 'main', :action => 'login'
@@ -30,7 +42,7 @@
     unless user.roles.detect { |role|
 	role.rights.detect{ |right|
 	  right.controller == self.class.controller_name and
-	    (right.action == 'all' or right.action == action_name)
+          (right.action == 'all' or right.action == action_name)
 	}
       }
       flash[:notice] = 'You are not authorized to view the page you requested'
diff --git a/app/controllers/configurations_controller.rb b/app/controllers/configurations_controller.rb
new file mode 100644
--- /dev/null
+++ b/app/controllers/configurations_controller.rb
@@ -0,0 +1,20 @@
+class ConfigurationsController < ApplicationController
+
+  before_filter :authenticate
+  before_filter { |controller| controller.authorization_by_roles(['admin'])}
+
+  in_place_edit_for :configuration, :key
+  in_place_edit_for :configuration, :type
+  in_place_edit_for :configuration, :value
+
+  def index
+    @configurations = Configuration.find(:all,
+                                         :order => '`key`')
+  end
+
+  def reload
+    Configuration.reload
+    redirect_to :action => 'index'
+  end
+
+end
diff --git a/app/controllers/main_controller.rb b/app/controllers/main_controller.rb
--- a/app/controllers/main_controller.rb
+++ b/app/controllers/main_controller.rb
@@ -11,7 +11,13 @@
   end
 
   def login
+    saved_notice = flash[:notice]
     reset_session
+    flash[:notice] = saved_notice
+
+    @title = Configuration['ui.front.title']
+    @welcome = Configuration['ui.front.welcome_message']
+
     render :action => 'login', :layout => 'empty'
   end
 
diff --git a/app/helpers/application_helper.rb b/app/helpers/application_helper.rb
--- a/app/helpers/application_helper.rb
+++ b/app/helpers/application_helper.rb
@@ -19,6 +19,11 @@
 
     # general options
     append_to menu_items, '[Settings]', 'users', 'index'
+
+    if (user!=nil) and (user.admin?) 
+      append_to menu_items, '[Site config]', 'configurations', 'index'
+    end
+
     append_to menu_items, '[Log out]', 'main', 'login'
 
     menu_items
diff --git a/app/helpers/configurations_helper.rb b/app/helpers/configurations_helper.rb
new file mode 100644
--- /dev/null
+++ b/app/helpers/configurations_helper.rb
@@ -0,0 +1,2 @@
+module ConfigurationsHelper
+end
diff --git a/app/models/configuration.rb b/app/models/configuration.rb
new file mode 100644
--- /dev/null
+++ b/app/models/configuration.rb
@@ -0,0 +1,43 @@
+class Configuration < ActiveRecord::Base
+
+  @@configurations = nil
+
+  def self.get(key)
+    if @@configurations == nil
+      self.read_config
+    end
+    return @@configurations[key]
+  end
+
+  def self.[](key)
+    self.get(key)
+  end
+
+  def self.reload
+    self.read_config
+  end
+
+  def self.clear
+    @@configurations = nil
+  end
+
+  protected
+  def self.read_config
+    @@configurations = {}
+    Configuration.find(:all).each do |conf|
+      key = conf.key
+      val = conf.value
+      case conf.value_type
+      when 'string'
+        @@configurations[key] = val
+
+      when 'integer'
+        @@configurations[key] = val.to_i
+
+      when 'boolean'
+        @@configurations[key] = (val=='true')
+      end
+    end
+  end
+  
+end
diff --git a/app/views/configurations/index.html.haml b/app/views/configurations/index.html.haml
new file mode 100644
--- /dev/null
+++ b/app/views/configurations/index.html.haml
@@ -0,0 +1,26 @@
+- content_for :head do
+  = javascript_include_tag :defaults
+
+%h1 Grader configuration
+
+%table
+  %tr
+    %th Key
+    %th Type
+    %th Value
+
+  - @configurations.each do |conf|
+    - @configuration = conf
+    %tr
+      %td
+        = in_place_editor_field :configuration, :key, {}, :rows=>1
+      %td
+        = in_place_editor_field :configuration, :value_type, {}, :rows=>1
+      %td
+        = in_place_editor_field :configuration, :value, {}, :rows=>1
+
+%br/
+= link_to '[Reload configuration]', :action => 'reload'
+%br/
+Your config is saved, but it does not automatically take effect.
+You must reload.
diff --git a/app/views/main/login.rhtml b/app/views/main/login.rhtml
--- a/app/views/main/login.rhtml
+++ b/app/views/main/login.rhtml
@@ -1,6 +1,6 @@
-<h1>Grader</h1>
+<h1><%= @title %></h1>
 
-<b>Welcome back!</b><br/>
+<b><%= @welcome %></b><br/>
 Please login to see the problem list.<br/><br/>
 
 <% if flash[:notice] %>
diff --git a/config/environment.rb.SAMPLE b/config/environment.rb.SAMPLE
--- a/config/environment.rb.SAMPLE
+++ b/config/environment.rb.SAMPLE
@@ -62,6 +62,3 @@
 # These are where inputs and outputs of test requests are stored
 TEST_REQUEST_INPUT_FILE_DIR = RAILS_ROOT + '/data/test_request/input'
 TEST_REQUEST_OUTPUT_FILE_DIR = RAILS_ROOT + '/data/test_request/output'
-
-# Uncomment this for single user mode (only root is allowed to log in)
-# SINGLE_USER_MODE = true
diff --git a/db/migrate/022_create_configurations.rb b/db/migrate/022_create_configurations.rb
new file mode 100644
--- /dev/null
+++ b/db/migrate/022_create_configurations.rb
@@ -0,0 +1,37 @@
+class CreateConfigurations < ActiveRecord::Migration
+  def self.up
+    create_table :configurations do |t|
+      t.column :key, :string
+      t.column :value_type, :string
+      t.column :value, :string
+      t.timestamps
+    end
+
+    Configuration.reset_column_information
+
+    Configuration.create(:key => 'system.single_user_mode',
+                         :value_type => 'boolean',
+                         :value => 'false')
+
+    Configuration.create(:key => 'ui.front.title',
+                         :value_type => 'string',
+                         :value => 'Grader')
+
+    Configuration.create(:key => 'ui.front.welcome_message',
+                         :value_type => 'string',
+                         :value => 'Welcome!')
+
+    Configuration.create(:key => 'ui.show_score',
+                         :value_type => 'boolean',
+                         :value => 'true')
+
+    Configuration.create(:key => 'contest.time_limit',
+                         :value_type => 'string',
+                         :value => 'unlimited')
+
+  end
+
+  def self.down
+    drop_table :configurations
+  end
+end
diff --git a/db/schema.rb b/db/schema.rb
--- a/db/schema.rb
+++ b/db/schema.rb
@@ -9,7 +9,15 @@
 #
 # It's strongly recommended to check this file into your version control system.
 
-ActiveRecord::Schema.define(:version => 21) do
+ActiveRecord::Schema.define(:version => 22) do
+
+  create_table "configurations", :force => true do |t|
+    t.string   "key"
+    t.string   "value_type"
+    t.string   "value"
+    t.datetime "created_at"
+    t.datetime "updated_at"
+  end
 
   create_table "grader_processes", :force => true do |t|
     t.string   "host",       :limit => 20
diff --git a/spec/controllers/main_controller_spec.rb b/spec/controllers/main_controller_spec.rb
--- a/spec/controllers/main_controller_spec.rb
+++ b/spec/controllers/main_controller_spec.rb
@@ -14,27 +14,27 @@
                        :source => 'sample source',
                        :compiler_message => 'none')
     @user = mock(User, :id => 1, :login => 'john')
-    Submission.should_receive(:find).with(@user.id.to_s).and_return(@submission)
+    Submission.should_receive(:find).with(@submission.id.to_s).and_return(@submission)
   end
 
   it "should let user sees her own source" do
-    get 'source', {:id => 1}, {:user_id => 1}
+    get 'source', {:id => @submission.id}, {:user_id => 1}
     response.should be_success
   end
 
   it "should let user sees her own compiler message" do
-    get 'compiler_msg', {:id => 1}, {:user_id => 1}
+    get 'compiler_msg', {:id => @submission.id}, {:user_id => 1}
     response.should be_success
   end
 
   it "should not let user sees other user's source" do
-    get 'source', {:id => 1}, {:user_id => 2}
+    get 'source', {:id => @submission.id}, {:user_id => 2}
     flash[:notice].should =~ /[Ee]rror/ 
     response.should redirect_to(:action => 'list')
   end
 
   it "should not let user sees other user's compiler message" do
-    get 'compiler_msg', {:id => 1}, {:user_id => 2}
+    get 'compiler_msg', {:id => @submission.id}, {:user_id => 2}
     flash[:notice].should =~ /[Ee]rror/ 
     response.should redirect_to(:action => 'list')
   end
diff --git a/spec/models/configuration_spec.rb b/spec/models/configuration_spec.rb
new file mode 100644
--- /dev/null
+++ b/spec/models/configuration_spec.rb
@@ -0,0 +1,90 @@
+
+require File.dirname(__FILE__) + '/../spec_helper'
+
+describe Configuration do
+
+  before(:each) do
+    @int_config = mock(Configuration,
+                       :id => 1,
+                       :key => 'mode',
+                       :value_type => 'integer',
+                       :value => '30')
+
+    @string_config = mock(Configuration,
+                          :id => 2,
+                          :key => 'title',
+                          :value_type => 'string',
+                          :value => 'Hello')
+
+    @boolean_config = mock(Configuration,
+                           :id => 3,
+                           :key => 'single_user_mode',
+                           :value_type => 'boolean',
+                           :value => 'true')
+  end
+  
+  it "should retrieve int config" do
+    Configuration.should_receive(:find).once.with(:all).
+      and_return([@int_config, @string_config, @boolean_config])
+
+    Configuration.clear
+    val = Configuration.get('mode')
+    val.should == 30
+  end
+
+  it "should retrieve boolean config" do
+    Configuration.should_receive(:find).once.with(:all).
+      and_return([@int_config, @string_config, @boolean_config])
+
+    Configuration.clear
+    val = Configuration.get('single_user_mode')
+    val.should == true
+  end
+
+  it "should retrieve string config" do
+    Configuration.should_receive(:find).once.with(:all).
+      and_return([@int_config, @string_config, @boolean_config])
+
+    Configuration.clear
+    val = Configuration.get('title')
+    val.should == "Hello"
+  end
+
+  it "should retrieve config with []" do
+    Configuration.should_receive(:find).once.with(:all).
+      and_return([@int_config, @string_config, @boolean_config])
+
+    Configuration.clear
+    val = Configuration['title']
+    val.should == "Hello"
+  end
+
+  it "should read config table once" do
+    Configuration.should_receive(:find).once.with(:all).
+      and_return([@int_config, @string_config, @boolean_config])
+
+    Configuration.clear
+    val = Configuration.get('title')
+    val.should == "Hello"
+    val = Configuration.get('single_user_mode')
+    val.should == true
+    val = Configuration.get('mode')
+    val.should == 30
+  end
+
+  it "should be able to reload config" do
+    Configuration.should_receive(:find).twice.with(:all).
+      and_return([@int_config, @string_config, @boolean_config],
+                 [mock(Configuration,
+                       :key => 'title', :value_type => 'string',
+                       :value => 'Goodbye')])
+
+    Configuration.clear
+    val = Configuration.get('title')
+    val.should == "Hello"
+    Configuration.reload
+    val = Configuration.get('title')
+    val.should == "Goodbye"
+  end
+
+end
diff --git a/test/fixtures/configurations.yml b/test/fixtures/configurations.yml
new file mode 100644
--- /dev/null
+++ b/test/fixtures/configurations.yml
@@ -0,0 +1,7 @@
+# Read about fixtures at http://ar.rubyonrails.org/classes/Fixtures.html
+
+# one:
+#   column: value
+#
+# two:
+#   column: value
diff --git a/test/functional/configurations_controller_test.rb b/test/functional/configurations_controller_test.rb
new file mode 100644
--- /dev/null
+++ b/test/functional/configurations_controller_test.rb
@@ -0,0 +1,8 @@
+require File.dirname(__FILE__) + '/../test_helper'
+
+class ConfigurationsControllerTest < ActionController::TestCase
+  # Replace this with your real tests.
+  def test_truth
+    assert true
+  end
+end
diff --git a/test/unit/configuration_test.rb b/test/unit/configuration_test.rb
new file mode 100644
--- /dev/null
+++ b/test/unit/configuration_test.rb
@@ -0,0 +1,8 @@
+require File.dirname(__FILE__) + '/../test_helper'
+
+class ConfigurationTest < ActiveSupport::TestCase
+  # Replace this with your real tests.
+  def test_truth
+    assert true
+  end
+end