Marketo accepts any HTML code that we write in Dreamweaver or Adobe Edge. However, even if the landing page appears correctly in browsers, it may not render properly when you paste the code in Marketo Design Studio. The best practice is to create the landing page in Design Studio itself by dragging and dropping each element of the landing page. This should be easy for simple pages but if you have a complex landing page, my team can surely assist you in fixing this up. You can connect with me at alok@grazitti.com.