Hi Reza,
Thank you for your question. Please try using the website with Google Chrome (https://www.google.com/intl/en-CA/chrome/browser/). This is the most ‘trouble free’ browser online today. Also, please close any high bandwidth programs such as torrent downloads. If you continue to have problems, please take a screen shot and describe it in detail, so I can help you further.
-“Your success is our success”
Also, have a look around the forum to see how other students have solved this issue. All the best.
aeadmin