do not bother computing width of images

layouts/partials/image.html

@@ -9,13 +9,12 @@
         		{{ printf "%s %dw" .RelPermalink .Width }}
     		{{- end -}}"
 
-    	sizes="
-    		{{- with (.Resize "600x q40") -}}
-    			{{- printf "(max-width: 700px) %dpx," .Width -}}
-    		{{- end -}}
-    		800px"
+    	sizes="(max-width: 900px) 600px, (min-width: 901px) 1200px"
 
-        src="{{ (.Resize "1200x q65").RelPermalink }}"
+    	src="
+    	{{- with (.Resize "600x q40") -}}
+    		{{ .RelPermalink }}
+    	{{- end -}}"
 	{{ end }}
     alt="{{ .alt }}"
 >