I posted a Forum topic about this a while back, and I thought it was cool enough to make into an Instructable. Kudos to NachoMahma for figuring this out.
This Instructable will show you how to add an extension to Firefox that lets you search for any word on a web site on Instructables. It's fairly simple, but still cool.
Step 1: Install Dictionary Search
Step 2: Set for Instructables Search
After restarting Firefox to install Dictionary Search, go to Tools>Add-ons. Dictionary Search should be the first one listed, so just click Options.
The first box, labeled "Text," is what is displayed on the submenu. "$" is whatever word or words you highlighted before right-clicking. I just used the text that NachoMahma suggested: Search Instructables for "$".
The second box, labeled "URL," tells it where to search. To search Instructables.com for Instructables containing the selected text, enter https://www.instructables.com/tag/?q=$&limit%3Atype%3Aid=on&type%3Aid=on&type%3Auser=on&type%3Acomment=on&type%3Agroup=on&type%3AforumTopic=on&sort=none. To search the whole site for everything, enter https://www.instructables.com/tag/?sort=none&q=$&limit%3Atype%3Aid=on&limit%3Atype%3Acomment=on&limit%3Atype%3Auser=on&limit%3Atype%3Agroup=on&limit%3Atype%3AforumTopic=on&limit%3Atype%3AforumComment=on.
Step 3: Use
This works the same way as the "Search Google for "Such-and-Such" option that is part of Firefox.
Let's say you were on Sporty's looking at an interesting-but-expensive air conditioner. You decide to see if there's a better option on Instructables, so you do an Instructables search, and get a page full of results. Hmmm...That third one looks nice...