Question

My understanding is floated elements must have their widths specified, or else unpredictable rendering may ensure.

Is this true/false?

Is it acceptable to float elements like DIVs and not specify widths?

Answer 1

Not including a width on a floated element is unpredictable because the browser is left to determine how wide your float is.

Theoretically, a floated element with an undefined width should shrink to the widest element within it. This could be a word, a sentence or even a single character – and results can vary from browser to browser. Source: http://css.maxdesign.com.au/floatutorial/introduction.htm