Scroll speed in Classilla

[MacOS Plus]

  I don't know if this is directly a function of Classilla's codebase or not, but some websites (ie. MacOS9Lives.com) will scroll quickly and smoothly, while others are very sluggish.  One site in particular was even worse with javascript enabled.  The difference is striking on the slow ones and reminds me of what it's like to use an unaccelerated video card.

  Any thoughts on this?  It's frustrating how it can be so good sometimes but not others.  I'm aware of all the established limitations about loading and displaying websites properly on outdated code.  I'm specifically interested only in what is slowing down the scrolling on certain pages.

Edit:
  I did a test on one offending page where I went into the Appearance settings and prevented loading of background images.  The page loaded nearly devoid of any graphics and colours whatsoever, but the scrolling was fine when viewing it that way.  Is this an issue with the browser engine itself or is it video card/driver related?

  I must say that I'm amazed by how fast the MacOS9Lives.com forum loads in Classilla, even on slow machines.  The graphical home page even loads fast.  Whatever you guys are doing with the coding, it's most definitely working!!!

[geforceg4]

depends on loaded assets
but mostly its because of bad javascript
most modern day websites are done very sloppily when it comes to
resources + client side scripting