As since version 2.0, this doesn't work :
class PostController < ApplicationController
Because there's no dynamic scaffolding in newer versions. So if you are using Ruby 2.0 or higher, all the tutorials you read will fail.
When you run the generator, select 'scaffold' rather than model, and type your "Link url:string description:text" into the "Model Name" box. This will generate a controller for you called links_controller.rb (and lots of other files)
Then Right click the project node again and click select Migrate Database > To Current Version. This will create the relevant database table and ruby scripts.
Additionally, routes.rb is under Configuration, not Configuration/Environments as stated, and you don't need to edit it, the scaffold generator did that for you. The url is now ...localhost.../links, although you can always type "Post" in the scaffold generation to change this back.
To add the tags field, right click the Database Migrations node, select Generate, then type "NewTagsField tags:string", OK, (this generates your 002_new_tags_field.rb) and then do the DB mIgrate thing again.
At this point you must either add code, or just regenerate your scaffold using "Link url:string description:text tags:string".
A quick tip for newcomers to the Netbeans IDE, get into the habit of running your project by right clicking the project node and selecting 'Run', because pressing the big green play button will not always run the current project. Netbeans has a few gotchas, but it's worth sticking with it. (Eclipse makes me want to set my own hair on fire.)
I fell heavily into the trap of version differences when I started getting into rails (last week), and it's a shame to see El Reg propagating the misery. Next time, Pan, maybe you could make sure that your tutorial will work on the latest version of the software you're talking about, since this is likely to be the version that newcomers will have installed.
In fairness though, 2.0 was only released in December, and the lack of backwards compatibility is catching a lot of people out.