Dreamweaver Design View does not support modern CSS standards very well sometimes. To work around some of the more egregious shortcomings, we included a special Design Time style sheet in your p7affinity folder. To deploy it, follow these steps:
Choose Format > CSS Styles > Design-time...
The Design-Time Style Sheets window will open.
Click the plus sign above the Show only at design time box and browse to the p7affinity-DT.css file in your p7affinity folder.
This needs to be done for each page you want to "fix". Dreamweaver does not have a facility to apply DT style sheets site-wide.
Choose from the following DMM tutorials.
Covers each rule in the DMM style sheet, including the responsive media queries.