Prefetching resources

hi my name is Sean brenaman and I'm a software engineer on Picasso web albums image files take longer to download than most kinds of files on the web but users want to look at large photos as quickly as possible on Picasso web we use a lot of tricks to make downloading photos as fast as possible one of the tricks we use is prefetching most of the files that we download are compressed image files we can't do anything about how large they are and they're going to take time over the network to come over but the sooner that we make the request the sooner the file gets there if we make the request at the beginning of an HTML page then as that image file loads all of the smaller files will load and everything will get to the user at about the same time on Picassa web albums we have good usage data where we know that if a user looks at one photo they're probably going to look at the next photo and maybe even the next one so we start downloading those ahead of time by the time they start looking at the photo it's already in the browser's cache that way the page loads instantly the files are already cached and the user can look at more content more quickly a couple of things you want to make sure of uh the files cach well in the browser excellent examples of this are image files JavaScript files stylesheets be careful about how much data you request you don't want to download your entire site you want to download a few resources to make loading that next page a little bit faster this technique doesn't work on every kind of website but where it can be applied it's a huge speed up for your users for more tips go to code.google.com/speed