Please provide a screenshot.
https://support.mozilla.org/en-US/kb/how-do-i-create-screenshot-my-problem

It is best to use a compressed image type like PNG or JPG to save the screenshot and make sure that you do not exceed a maximum file size of 1 MB.

Then use the Browse .... button below the Post a Reply text box to upload the screenshot.

Hello,

    First of all mention the screen shot of your actual problem,,and second thing if you are using mouse then you have wheel,so you can enlarge the text or to zoom in the your browser's window.

hope may be helpful,,,