I am looking for an addon to install so that when you select a word in a webpage ( by clicking) it automatically highlights all the instances of that selected words in that
Ok C Graphics man here's the code
Ok its real easy you don't even have to write another function. Here's the code to highlight any word in the current tab.
gBrowser.selectedTab.linkedBrowser.finder.highlight(true, 'YOUR_WORD_HERE')
if you want to unighlight then set the first argument to false.
You can do this in any tab just have to supply the browser element within the tab.
like this code here will highlight everything in the first tab:
gBrowser.tabContainer.childNodes[0].linkedBrowser.finder.highlight(true, 'YOUR_WORD_HERE');