Opera has a few “special” pages which give you configuration information and some other related “stuff” Some of these are useful for debugging, some for information, and some helps you retrace your steps. Simply type these into URL field of the addressbar or press F2. (Note: do not put http:// before these. They will not work if you do.) 

<dt><a href="opera:about">opera:about</a></dt>
<dd>Gives you all the information that you need for finding our about where certain files are found.  For example if someone suggests that you edit your <a href="http://www.opera.com/support/usingopera/operaini/">opera.ini</a> or your <a href="http://operalover.tntluoma.com/8/" title="FIX URL HERE">search.ini</a> but where are they?  Or what if you want to backup your Opera installation?  Where are your personal files (bookmarks, contacts, <a href="http://operalover.tntluoma.com/8/" title="FIX URL HERE">Notes</a>, etc) stored?  <a href="opera:about">opera:about</a> will tell you.  Also information about what version and build you are using</dd>

<dt><a href="opera:cache">opera:cache</a></dt>
<dd><p>

Shows you the local copies of files which Opera has stored from web pages you have visited. In the left column is the name of the local file, in the middle column is the size in bytes, and in the right column is the original URL. Why on earth would you care? Well, if you have visited a page with an embedded movie (QuickTime, Flash, etc) you can look here and see what it is called, then open up your cache folder and copy it from there to your Desktop or wherever you want to save it.

“But wait!” you protest, “All this does it tell me the filename, it doesn’t give me the option to open the file or save it locally.” Yes, you’re right. Wouldn’t this be the perfect place to have those files linked so you could right click on the link and then open the file or save it somewhere else? Well yes, it would, but unfortunately that isn’t implemented (yet?). However, once you know the location of your Cache folder, you can easily find it there. And how do you find out where your Cache folder located? opera:about of course!

Advanced tip: Go to File → Work Offline and you can click on the URLs in opera:cache and have the local copy opened. 

<dt><a href="opera:history">opera:history</a></dt>
<dd>I include this for completeness sake (and to avoid having people tell me that I forgot it) but it isn&#8217;t very useful compared to Tools &rarr; History which has a quick search feature.</dd>


<dt><a href="opera:plugins">opera:plugins</a></dt>
<dd>Plugins (most notably Flash, but also QuickTime, Shockwave, etc) control some of the content that we love (and hate) about the web.  To view this content, you need the appropriate plugin.  This page shows what Opera has found to be installed.  If you are having problems getting something to run, be sure that Opera finds the appropriate plugin.</dd>

None of these features are enough to make anyone switch to Opera, but they are handy tools to have when you are using Opera and need to do some troubleshooting.