Via Jeffry Zeldman’s alter ego Apartness’ blog come the following practices from Tanya Rabourn regarding web standards (emphasize mine):

In order to anticipate future browser compatibility we require conformance to the following W3C standards:

HTML

Validate to either the W3C’s XHTML 1.0 transitional or strict doctype http://www.w3.org/TR/xhtml1/

CSS

Validate to the W3C’s CSS 2.1 or 1.0 http://www.w3.org/TR/CSS21/ http://www.w3.org/TR/CSS1

Javascript

Javascript will never use browser detect but instead object detection to test for browser support of properties, arrays and methods

I think we all know that things aren’t black and white, just how it is in this case. Object detection surely is a good idea: if you want to fetch an element which has a certain ID, you need document.getElementById, so you might as well want to make sure that method is supported before you run your script. Unfortunately browsers have other bugs than “simply” not supporting DOM methods.

Take Safari, for instance. It won’t repaint the document if you append a new node to it. To work around this you need to use a hack which adds an empty string to the innerHTML of the node you just appended to. Quite obviously you don’t want to use this hack in other browsers: you need to use browser detection to determine if the hack is necessary. And to add to the confusion: this bug has been solved in Safari 1.3, so you might as well want to make sure not to use this hack in that browser.

By the way, did I mention innerHTML is not supposed to work in XHTML documents? You need to find a way to detect that as well…

To conclude: it’s a good idea to use object detection, but sometimes it just won’t cut it. And you don’t want to leave out awesome scripts because it uses browser detection, do you?