Are these style recognized by all browsers of all versions?

#parent div { float:right; }
#parent > div { float:right; }

Most important开发者_JAVA百科ly:firefox and IE

No. Some browsers don't support CSS at all (lynx for example).

The glib answer aside, among browsers you probably care about, the child selector is not supported in Internet Explorer 6.

See this chart:

#parent > div is supported by ALL browsers EXCEPT IE6.

See Quir}{smode's master compatibility table for answers to all these types of questions.

Click here for the CSS Compatibility table