I've figured out how to get Opera Mobile 10 Beta 3 to only display websites in desktop view without getting redirected to a mobile version of the site. UPDATE:
Works in Opera 10 Final too!
The first 2 steps are pretty common knowledge, but they don't work for all sites. It's the 3rd step that makes every website work for me.
Step 1: Set a custom user agent string
This tells websites what kind of device you are using to browse the site (desktop computer, smartphone, etc).
Goto opera:config -> User Prefs -> Custom User-Agent
Find a desktop user agent string, type it in, and save. I'm using the one from my Firefox browser on my home desktop (it can be found by clicking Help -> About Mozilla Firefox). Mine looks like this:
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)
You can use whatever string you can find that works. I've even seen people use an iPhone user agent to get iPhone versions of websites.
Step 2: Spoof a user agent ID
This tells websites what client you are using.
Goto opera:config -> User Agent -> Spoof User Agent ID
Type in the number corresponding to a browser to identify as that browser
1 = Opera
2 = Mozilla
3 = Internet Explorer
4 = Mozilla, Opera not mentioned
5 = Internet Explorer, Opera not mentioned
Don't forget to save. I have mine set to 2, so websites think I'm using Firefox
Step 3: Set custom HTTP_Accept parameters
This one is hard to explain, but it basically tells the website which versions (i.e. desktop or mobile) are acceptable for viewing.
Goto opera:config -> Network -> HTTP Accept
Type this in exactly:
text/html, application/xml;q=0.9, application/xhtml+xml, application/x-obml2d, multipart/mixed, image/png, image/jpeg, image/gif, image/x-xbitmap, */*;q=0.1
Please note that this is just the default entry minus the one element that allows for mobile/wap viewing.
Also in the Network section, go to HostName Expansion Prefix and delete wap from the list. Remember to save. Exit the browser and everything should work like a desktop from now on! You can go to www.whatsmyuseragent.com
to check and see if everything is right. If you still want to view mobile versions of sites, you'll have to type in the specific mobile URL for that site (I keep mobile versions of my bookmarks just in case I get stuck on EDGE or a slow connection).
Hope this helps! If anyone with web-coding experience would like to explain further or correct anything I did wrong, please be my guest!