- The number of possible simultaneous connections in a browser
- IE browser has memory leaks when doing complex operations
By default a browser supports only up to 2 simultaneous connections as described by Michael Schwartz in this blog entry. It is possible to increase this amount through a registry setting. Good to increase the amount of simultaneous downloads, but not something you can count on in yor application. This means that you should really watch out in implementing multiple separate XmlHttpRequests from your web page. Although I assume that calls are just blocked when the “request queue” is full, and will be executed when a previous request is finished. I thought that applications in Flash could work around that limitation, but as far as I know Flash utilizes the browser HTTP stack, so will probably suffer from the same restrictions (can someone confirm this?).
IE memory leaks:
Something that really “shocked” me a while ago was this weblog post by (again) Michael Schwartz. He describes memory leaks with XmlHttpequests in sites like http://www.start.com. I didn’t hear much about it after that post, until I stumbled over a blog entry by Telerik (the developers of the great WYSIWYG HTML editor). They describe IE memory leaks, and some tips on how to avoid them. They link to this article at http://quirksmode.com with more pointers to information on IE memory leaks.
Lets hope that implementations like Ajax.Net, MagicAjax and Atlas and all the other Ajax libraries work around these issues so we simple developers don’t have to take care of all the quirks that the different browsers will definitly have. This is one of the reasons why Flash looks so interesting: one vendor, so probably the same bugs on all platforms;-)