What do you tend to roll with: classes (.) or id's (#)?

I've always used a majority of id's in my css, but should I maybe use more classes for their flexibility? Is there a downside to predominantly using classes in stylesheets?

It entirely depends on a) the size of the site b) the complexity of the design and c) the purpose of each class etc.

Ordinarily I use ID's for basic layout, when I'll only be defining each section once. But for a more complex layout, I'll switch to classes, so I can reuse elements and only declare them once in a stylesheet.

For example, with rounded corners. I normally declare a class .round that I can then apply to anything throughout the site. Text colours as classes too.

You may be interested in reading this article:
http://css-tricks.com/the-difference...-id-and-class/

Thanks guys. Guess the way I'm styling is right (i.e. use classes where appropriate and the same goes for id's) .