What causes lazy/laggy scrolling in CSS?

I have a design I'm creating in CSS, and it has started to sort of, er, lazy scroll. By that I mean the scrollbar lags a bit when you are scrolling. What are common causes of this so that I can debug it from my site?

EDIT:

The document has very little content (not even a paragraph开发者_StackOverflow), so not much at all. No flash, two images.

EDIT:

I feel so stupid. Improperly formatted background: property was causing the issue. Thanks nonetheless, everyone.

It's likely to be due to heavy processing requirements via css.

(CSS does affect scrolling in every browser) I have seen this scenario many times (the worst case is with SVG). It usually hits browsers like Chrome hard because of it's AA.

There was a great website that detailed the heaviest to the safest properties to use in regards to CSS effects, sorry I don't have the link. Though from my experience I would say to consider:

Gradients: The more you feature or the larger the area they cover the more exponential the rendering calculations. Abusing stops and additional colors also adds to the mayhem.

Border-Radius: Is usually clipping off its internal content whatever it may be. I've noticed differences when excluded.

Opacity can be the main issue if coupled with other css effects. In certain scenarios I've found great improvements when removing opacity or reducing it's usage. As it's not just transparency it's driving it's also for some browsers anti-aliasing text.

Images: The way images can affect scrolling should be obvious, though I've discovered re-sizing imaged from it's native resolution can become a more noticeable factor.

Use of properties such as background-size:; draws huge power in certain situations, a workaround could be to scrap the div, replace with < img > and overlay with a blank div containing text/ content.

Animations transitions & translations are obvious power eaters if abused, especially animation that loops continuously or re-sizes to the browser via percentages.

Bare in mind someone on a low spec celeron PC will have a terrible experience on a site that lags on your reasonably/ high powered PC/ mac