Classes in tag

I have created an email theme, but as soon as I try to edit this with the builder it adds extra code to the <html> tag:

style="" class=" js flexbox flexboxlegacy canvas canvastext webgl no-touch geolocation postmessage no-websqldatabase indexeddb hashchange history draganddrop websockets rgba hsla multiplebgs backgroundsize borderimage borderradius boxshadow textshadow opacity cssanimations csscolumns cssgradients no-cssreflections csstransforms csstransforms3d csstransitions fontface generatedcontent video audio localstorage sessionstorage webworkers applicationcache svg inlinesvg smil svgclippaths js csstransforms csstransforms3d csstransitions responsejs "

Is there a way to prevent this from happening?