Weird character  inserted with CKEditor

This bug occurs whenever you add a whitespace between two characters/words. It also affects lines separated by a blank line as in CKEditor the default behavior of dealing with blank line is to insert a whitespace character in it.

This is caused by the default character encoding incompatible with CKeditor's. To fix it, go to your theme's template folder(the default is main, you may want to do the same for acp theme), open the file header.tpl and add this following line right below the <header> opening tag:

This will change the encoding to UTF-8 and should fix your problem. Note if you use multiple themes, you will have to add this meta statement in all themes.