Will targeting IE8 with conditional comments work?

[*]

One thing to note:

It does work, BUT if you are loading the page/site local network (e.g. Intranet) it will load in IE7 mode by default! (update – localhost[*] is a special case, that does render in standards mode)

This goes against MSFT’s original statement of going STANDARDS by default.

e.g.

http://127.0.0.1/mysite/mypage.php  <-- IE8 by default (updated!)
http://localhost/mysite/mypage.php  <-- IE8 by default (updated!)
http://machinename/mysite/mypage.php  <-- IE7 by default
http://192.168.100.x/mysite/mypage.php  <-- IE7 by default
http://google.com/  <-- IE8 by default

[*] – Scott Dickens [MSFT] noted in a comment here on the IE Blog that localhost was a special scenario in the Intranet (often used to develop Internet sites) thus would render in Standards mode by default.

To test what mode a page in IE8 is really rendering in, you can use check the developer tools or use this bookmarklet code (only works in IE8):

javascript:
var vMode=document.documentMode;
var rMode="IE5 Quirks Mode";
if(vMode==8){
  rMode="IE8 Standards Mode";
} else if(vMode==7){
  rMode="IE7 Strict Mode";
}
alert('Rendering in: '+rMode);