[header] How to zoom in on firefox [title] Launch a session of firefox and navigate to the web page you want magnified. [title] Click on the firefox menu button located at the top right corner of your firefox session. [step] The firefox menu button features three horizontal lines. 
[title] Click on the plus sign one or more times as desired to zoom in on the content displayed on-screen. [step] You can magnify content by up to 300 percent.