Display errors can be caused by different issues:
1. Surfing with an old version of internet explorer. In that case you can download one of the following browsers:* Click here to download Google Chrome
2. Some display errors are caused by a corrupted cookie or something else in browser's cache. In that case try to clear it using one of these guides:
* Cache cleara guide for Chrime.
* Cache clear guide for Firefox.
3. In case you have a parent control program installed, you need to disable it while using Moodle.
4. Internet Rimon (an Israeli internet service provider) may sometimes filter certain contents on Moodle. In that case, you can contact their customer support.