Our Web site uses HTML 4, can we still use XStandard XHTML editor?
Yes, you can author your content in XHTML, using XStandard, and then insert it into an HTML 4 page layout. The advantage of authoring content in XHTML is that you are creating content that can be used now, in legacy page layouts such as HTML, and you are future-proofing the same content, because it can be used in future page layouts.
The illustration below shows an HTML page layout containing XHTML content generated by XStandard.