Web presenter content size within pixel width size

[RoseW Profile Private messageWebsite]

Saved as an html format so the file could be included in my website for an Australian friend to view.
I made the effort just for the friend because it is a HUGE file overall.
This isn't a thing I would do again anytime soon.
What I wondered is that the original image content size i.e. 1Mb or 850Kb is squished into the parameters set in the html format. (I changed the 800 x 600 to be in the 1025 range) since there is no actual change in the complete show file.
Since I didn't see any reference to resize the images for web content I wondered if images really should be prepared specifically using quality resizing in the external photo edit software in the same manner stand alone images are prepared for a personal website or photo forum.