Opera are trying to "simplify" the UI and so options like this are only available via editing the site prefs INI file manually. To do this:
1) In Opera, make a site-specific prefs entry for SiteX (context-menu > Edit site preferences...) via the UI. I normally remove the domain www to leave just the main site e.g. nytimes.com rather than
www.nytimes.com. Close Opera.
2) Go to your profile directory (look in opera:about to se where it is) and find override.ini. Open it in an editor of your choice.
3) Find the site you added, and append:
User Prefs|History Navigation Mode=#
# is
Automatic mode = 1 (uses heuristics to best guess)
Compatible mode = 2 (slow mode)
Fast mode = 3 (turbo mode!)
to that entry, for example:
[ebay.co.uk]
User Prefs|Ignore Unrequested Popups=1
User Prefs|Accept Cookies Session Only=0
User Prefs|Local CSS File=C:\Documents and Settings\styles\ebay.css
User Prefs|User JavaScript=0
User Prefs|Always Load User JavaScript=0
User Prefs|Enable Referrer=1
User Agent|Spoof UserAgent ID=1
User Prefs|History Navigation Mode=3
In this example, this forces Opera to use fast navigation for ebay.co.uk - so i ensure I get lightning fast navigation there no matter what my default global setting is :-) Setting the number to 2 uses the compatible mode - which I use for [mail.google.com]. I also add some personal modifications to the CSS (change link colours and fonts to my liking), turn off my UserJS (aka greasemonkey) scripts as I don't use them for EBay, and allow EBay to set permanent cookies (my default sets all cookies as session only). thos last options are fully available via the UI. Site-specific preferences rocks, and IINM it is coming to Firefox too in V3 :-)