Contents cannot be edited in chrome and IE web browsers

I'm using web site developed with Plone. The content in HTML format cannot be edited and showing blank in chrome browser.

And it is showing only source codes in IE browsers.

As I'm just the user (not developer) and thus I cannot fix inside the coding and please advise me how to fix/update the browser setting to edit those contents in Plone HTML content editor.

Thanks.

It might be due to the version of TinyMCE (the rich text editor used in Plone) you are using.
Current version is fine, but older one had a known bug.
Just upgrade to the last Plone 5.0 version, and it should be fixed.

Which version of Plone are you using?