Looking at the most recent questions that have been closed as off-topic, I see:
- A question on Drupal that probably should have been closed as NARQ
- An overly broad web development question
- A web app feature request
- A question on how easy it would be to install some software (presumably a web app); I think it should have been NARQ
- Asking for experiences in unsolicited contact of people through social media
- A question about building a Facebook app
- A question about Gmail on Android security (migrated to Android Enthusiasts)
- A question about integrating Google Play Music into a Linux music player
- A question about legal characters in email
- A question about integrating contacts on an Android phone with a task manager (migrated to Android Enthusiasts)
- A question on browser functionality (migrated to Super User)
- A request for web app recommendations for "lifetime" email addresses; probably should have been closed as NC
- A JavaScript error in someone's code
- A request for web app recommendations for a clothing store; should have been closed as NC
- A question about embedding reports in a web app someone is developing
- An app recommendation for translating PDFs; probably should have been closed as NC
- A request for a web app recommendation for community management; probably should have been closed as NC
- A programming issue with Google Maps
- A problem with a Facebook app being developed
- A question about email addresses with Salesforce.com. (There is apparently a saleforce.stackexchange.com)
- A request for a web app recommendation for data entry. I would expect NC
- A request for a web site so someone can re-build iGoogle
- A PHP programming question
- A question about playing audio in a web app being developed
- A question on how to get Microsoft Outlook to send/receive Gmail. Migrated to Super User
- A problem with putting a Facebook "Like" button on a web page. Migrated to Stack Overflow
- An overly broad JavaScript question. There's so little information, though, it could arguably have been closed as NARQ
- A request for recommendation of a website to "communicate" with contractors. NARQ or NC would have been better, I think
- A question about the security of third-party authentication in a custom web app. Migrated to Webmasters
- A question about code mysteriously appearing on a custom web site
- A JavaScript question. Migrated to Stack Overflow
- A request for recommendations of a simple online SQL database
- A question on a keyboard shortcut in Google Chrome
- A question about a hacked WordPress installation
- A question about Google's Pagespeed service for a custom app. Migrated to Webmasters
All of this is in addition to several successfully migrated questions (to Web Masters) asking about Google Search and SEO.
Clearly we need a custom reason:
you're asking a question about building a web application. Programming questions should go on [Stack Overflow]
Since we don't want to migrate "crap", we should probably also cover:
- SEO
- Maintaining your own site/installation
- Browsers and other desktop software
- Bug Tracker question: The question is more of a feature-request/bug report for the web app and is better asked as a question to the webapp developer
But otherwise I think (so far) the new reasons cover most issues.