Update Firefox Apocalypse.tid (#3007)

Type Exploer > Explorer

editions/tw5.com/tiddlers/platforms/Firefox Apocalypse.tid

@@ -18,7 +18,7 @@ There is a [[discussion thread|https://groups.google.com/d/topic/tiddlywiki/Lcld
 
 Firefox was first released in November 2004, a few months after the first version of TiddlyWiki. It was in many ways the Millenium Falcon to Microsoft's Death Star (in the shape of Internet Explorer). IE had by then enjoyed more than 5 years as the dominant browser, leading many in the web community to be frustrated that Microsoft's self-serving extensions to HTML had become de facto standards at the expense of innovation that might benefit the web community as a whole.
 
-Firefox quickly became successful because it managed to render web pages with close enough compatibly with Internet Exploer while offering a superior user experience. A large part of the promise of that user experience was the ability for any user to customise every aspect of the browser. Two innovations were behind this:
+Firefox quickly became successful because it managed to render web pages with close enough compatibly with Internet Explorer while offering a superior user experience. A large part of the promise of that user experience was the ability for any user to customise every aspect of the browser. Two innovations were behind this:
 
 * The entire user interface of the browser was constructed in [[XUL|https://en.wikipedia.org/wiki/XUL]], effectively an extension of HTML that enabled it to render conventional user interfaces (at the time, HTML was largely restricted to simple document-oriented layouts). Tweaking a few lines of XUL code could make wholesale changes to the user interface of the browser
 * The Mozilla add-on architecture gave full privileges to add-ons, enabling them to observe and interact deeply with the browser engine itself, and the file system of the computer on which it was running