Hi,
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,
Joe