Hi Mariana.

This warnings you're getting are but simple warnings indeed. They simply notify you that further improvements could be made to the code that WebSiteX5 generates but are to be taken very lightly. In order to solve these, you would need to manually intervene on the code that the software generates in order to publich the website online.

These improvements are very minimal and won't product any real effect on performance nor SEO for your website. This being said, the developers are still always working in order to make it so that the software can generate the most optimized code possible, and for this reason, I thank you for reporting this feedback here to us

Let me know if I can provide more insight on this 

Stefano