Keeping within acceptable limits

The 45-50KB target

Until everybody's on broadband and network logjams are a thing of the past (in other words for quite a long time yet), the optimum size of a web page is estimated to be no more than about 50KB. Research shows most people give up if a page does not appear on their screen within 20 seconds. Some people won't even wait that long. The 50KB target is not a hard and fixed rule, but a page that size would take about 15 seconds to download on a 28.8 modem. Not much time left to grab someone's attention.

Even though 28.8 modems are now becoming something of a rarity, particularly in industrialized countries, network logjams are not. Light, nimble sites are more likely to download quickly, and therefore have a better chance of grabbing attention.

So how many thumbnails can I safely add to a PA page?

First the bad news...

The Park Avenue page that has been used throughout this demonstration of ShowPic (portfolio2b.htm) weighs in at 53KB. So, on the face of it, the answer is none.

Now the good news...

One of the cleverest aspects of the PVII Park Avenue design (apart from its good looks) is the way it keeps bandwidth use to a minimum. All of the JavaScript for the extensions is in an external file, so too is most of the CSS style information. Together, these represent about 15KB, so in fact the real size of portfolio2b.htm is more like 68KB. But they are downloaded only once by each visitor - on the opening index page, which weighs in at a super-slim 23KB. The opening page bears the strain, allowing subsequent pages to be more liberal with graphics.

Park Avenue's use of library items means that many of the graphic elements of a page are used over and over again. Once downloaded, they too remain in the cache of the visitor's PC (a good reason for NOT setting your pages to refresh automatically every time they're accessed).

Nevertheless, although the thumbnails on Park Avenue average only 3KB each, there's not much much leeway to add more than 2 or 3 extra thumbnails and remain within the 50KB target. One solution, if you want more, is to not load the first full size image (as on the first page of this demonstration). To do this on an existing Park Avenue portfolio page, just remove the ShowPic behaviour from the body tag (onLoad). That would give room for an extra 4 or 5 - making 10 to 12 in all. That is probably more than enough. The average visitor is unlikely to want to scroll through endless thumbnails. If you're creating a specialist site, where you know the target audience well, you can make your own judgements about optimum numbers and download times.

How big can full size images be? The only limits are screen size, bandwidth and the patience of visitors faced by a long download of an unoptimized image.

Now break out of the box...