Reduce size of HTML5 help files

[#1]

Size of HTML5 help project

The result of the compilation of an HTML5 help project from Frame 2017 is 15 Mega

The dev team would like it to be smaller.  (the package I give them)

Graphics are small .png files

Are there any settings that can be changed to reduce the size of the files sets?

[#2]

Size of HTML5 help project

The result of the compilation of an HTML5 help project from Frame 2017 is 15 Mega

The dev team would like it to be smaller.  (the package I give them)

Graphics are small .png files

Are there any settings that can be changed to reduce the size of the files sets?

[#3]

It seems that some of the png files are not so small after all.

Are there reccomendations for how to reduce the size of such files?