Its possible that the WYSIWYG editor does that. We have both CKeditor and TinyMCE so you could try a different editor in site settings.
In the latest version of mojoPortal there is also a setting in the Html Content feature settings to disable the WYSIWYG editor and use a plain text area. By doing that you can enter the raw html that you want and nothing will be changed since the WYSIWYG editor is not used.
Hope that helps,