It seems more and more that web sites are using resource hungry java/flash scripts etc in their web pages.
These adversely effect PCs running at, say, less than 1Ghz CPU.
To relate a specific case.
I use Firefox for almost all my web browsing and this is with various desktops/laptops running Win98, WinNT and XP OS's.
The most resource hungry part of the QF site I frequently encounter is when doing online bookings from one of the "Specials" pages (e.g. Domestic Specials "From Melbourne") with a change to a selection box control or destination generating a myriad of changes to other controls and their loaded values. On my 550Mhz home PC I can actaully observe these changes being made.
The processing required by the script to set up a page, then continually monitor the controls/values and any changes being made to them meant that the scripts would often timeout before the initial setup process for the web page display completed.
In the end I did some research and ascertained how to get around this. I had to set the Firefox dom.max_script_run_time value up from it's default of 10 seconds to 30 before I could reliably use the site.
There other other site I have problems with; they include FOXTEL's New "you beaut" program guide (since Jan 1), many Telstra hosted sites such as Bigpond, Webmail, AFL.com.au & NRL.com.