Make sure that the HTML content is not copied and pasted from some other text editor (e.g. Microsoft Word). Note that Microsoft Word tends to insert a hidden code into a text which, when pasted into a web page using the WYSIWYG editor, can mess up the layout and cause internet browsers, such as Internet Explorer, to crash and/or produce an error.
To avoid it, create the necessary content directly in the WYSIWYG editor that is integrated in the default Mercium installation.
NOTE: If there is a lot of text content written using Microsoft Word, it is not necessary to rewrite it again in the WYSIWYG editor. Copying the content from Microsoft Word and pasting it into Notepad will remove all the unwanted code from the text. Then you can copy the text from Notepad and paste it into the WYSIWYG editor. This will provide a clean copy of the text that can be formatted properly from within Merchium.