problems with seeing backgrounds on some sites, including Facebook.

[SlimSylv]

How can I fix this, please, Using latest Firefox browser on a desktop, WIN XP PRO SP 3.0 32 bit
When I am on FF, I see mages, but not always the links to the postings.....I have so far managed, because my pointer changes when I hover over the link text....but on a new site, I don't always 'know' where the links are, on Wordpress blogs, for instance, the Facebook link doesn't show, but when I mouse over where it should be, I can usually share the post....Can you give me any help with this.
Also, I do not 'get' GitHub........I had to contact them to direct me to your page (?).
Very confusing
With gratitude, and kind regards
Sylvia