Image preloading issues

Do I optimize for sequence or deep links?

[Wilma]

In optimizing slide shows and tutorial pages so they load fast, I ran into this dilemma:

1. JavaScript can preload the next page's images after the current page finishes loading (script here [webmasterworld.com]), but only works if users have it turned on.
   
2. HTML preloading of images reduced to 1 x 1 pixel works in any browser. Speed is fine for users who follow a sequence. But if users drop into the middle of a slide show via a deep link, the first page will load two images at half the speed. So the first page these users see loads slow and gives them a bad impression. :(
   

My site's target audience includes overseas visitors with old computers on slow dialup connections. Maybe I worry needlessly: could boosting slide page size from 20 to 30 K, and initial DL time from 4 to 9 seconds or higher via method #2, have a significant effect on traffic? Would preloading that works for all visitors counterbalance that?

Better ideas, anyone?

[SEO practioner]

Hi Wilma and welcome to WW!

We're back to the $ 64k question I guess. We all know how hard it really is to please "ALL" visitors that come to any web site. I guess the best answer to that is finding a happy medium where most users would get a fairly good experience.

Java scripts can help, but are not the end all solutions at all times. On some days, a webmaster has to improvise. Maybe a solution you could ponder is this:

Try putting the js script on all of your pages that has that particular course or slide show you need. That way, if a visitor lands right in the middle of one of the slideshows either because he was sent to you from a search engine (always nice!) or simply because he choose it like that, at least his visiting experience should be enjoyable.

What is important in such a scenario is to always include a forward and back button, to help navigating in one direction or the other. You don't want them to come into a "dead-end" situation and loose them all together...

I hope that was of help to you

SEO :-)

[tedster]

I can't see an extra 4 to 9 seconds being too big a problem for users who are already well aware that they have a slow connection. If you do go with the HTML 1x1 preload, you can try putting the preload images in their own dedicated table at the end of the HTML document. Most browsers will prioritize the earlier images and give you an extra edge.

One other thing - I would avoid the progressive jpg format. Explorer's support for it is lousy. Browsers are supposed to render the blurry, early version first and fill in detail as the rest of the image data becomes available.

Instead, Explorer waits until the entire JPG image is there and renders it all at once. It leaves a totally blank image until everything can be seen.

It's better for users to see images being rendered chunk by chunk, in my opinion. So avoiding the progressive format gives your slow connection visitors an extra something that can hold them - they can see some of the image and know that something's happening.

[Wilma]

Thanks, Tedster. IE 5.1 Mac, which I use, does render progressive JPEGs okay, so I wasn't aware of that problem.

I'll try adding the table as you suggest.