diff --git a/app/models/user.rb b/app/models/user.rb
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -111,6 +111,7 @@
     begin
       http = Net::HTTP.new('www.cas.chula.ac.th', 443)
       http.use_ssl = true
+      http.verify_mode = OpenSSL::SSL::VERIFY_NONE
       result = [ ]
       http.start do |http|
         req = Net::HTTP::Post.new('/cas/api/?q=studentAuthenticate')
@@ -119,7 +120,7 @@
         result = JSON.parse resp.body
       end
       return true if result["type"] == "beanStudent"
-    rescue
+    rescue => e
       return false
     end
     return false
@@ -239,7 +240,7 @@
 
   def update_start_time
     stat = self.contest_stat
-    if (stat.nil?) or (stat.started_at.nil?)
+    if stat.nil? or stat.started_at.nil?
       stat ||= UserContestStat.new(:user => self)
       stat.started_at = Time.now.gmtime
       stat.save
diff --git a/app/views/graders/_grader.html.haml b/app/views/graders/_grader.html.haml
--- a/app/views/graders/_grader.html.haml
+++ b/app/views/graders/_grader.html.haml
@@ -2,10 +2,10 @@
 %td= grader.host
 %td= grader.pid
 %td= grader.mode
-%td= grader.updated_at.strftime("%H:%M:%S") unless grader.updated_at.nil?
+%td= grader.updated_at.strftime("%H:%M:%S") if grader.updated_at
 %td= grader.task_type
 %td
-  - if grader.task_id.nil?
+  - unless grader.task_id
     idle
   - else
     = link_to "#{grader.task_id}", :action => 'view', :id => grader.task_id, :type => grader.task_type
diff --git a/app/views/main/_submission_short.html.haml b/app/views/main/_submission_short.html.haml
--- a/app/views/main/_submission_short.html.haml
+++ b/app/views/main/_submission_short.html.haml
@@ -22,5 +22,5 @@
     = link_to("[#{t 'main.cmp_msg'}]", {:action => 'compiler_msg', :id => submission.id}, {:popup => true})
   = " | "
   = link_to("[#{t 'main.src_link'}]",{:action => 'source', :id => submission.id})
-  //= " | "
-  //= link_to "[#{t 'main.submissions_link'}]", main_submission_path(submission.problem.id)
+  = " | "
+  = link_to "[#{t 'main.submissions_link'}]", :action => 'submission', :id => problem_name
diff --git a/app/views/user_admin/user_stat.html.haml b/app/views/user_admin/user_stat.html.haml
--- a/app/views/user_admin/user_stat.html.haml
+++ b/app/views/user_admin/user_stat.html.haml
@@ -48,7 +48,7 @@
             %td= link_to sc[i].login, controller: 'users', action: 'profile', id: sc[i]
             %td= sc[i].full_name
             %td= sc[i].activated
-            %td= sc[i].try(:contest_stat).try(:started_at)!=nil ? 'yes' : 'no'
+            %td= sc[i].try(:contest_stat).try(:started_at) ? 'yes' : 'no'
             %td= sc[i].contests.collect {|c| c.name}.join(', ') 
             %td= sc[i].remark
           - else