Incomplete displays on some pages using Firefox and Windows IE

A reinstalled my Win 7 64bit OS a month ago. Since then I've found some web pages do not display the contents of buttons and banners. This happens whether I'm using Firefox or Win IE. I've updated both browsers, updated Flash, and updated Adobe reader.
Tech support from each browser said, "It ain't us".
Here is what I mean:

I contacted the website for this page (an edX course) and they couldn't replicate it; said it was a browser or system problem.
I have experienced this problem on other websites, including the main gmail site.
I think I've screwed up a setting in Windows 7 when I was reinstalling it. Whatever I did or didn't do, is interfering with both browsers (and who knows what else). I've got no clue.
Any advice would be much appreciated.
Thanks.

I appreciate the suggestions concerning how to fix my display problem(s). I've tried two of them.
I ran TFC from bleepingcomputer and while it located and disposed of 745 Mb of crap, it didn't correct the display problem.
I then purchased (!) RegCleanPro and ran it. It found and removed 50 crappy items in my registry, but the display problem persists.
While I have no actual clue, I wonder if the problem with the incomplete display of websites could in some way be due to some setup option that I chose (or didn't choose) when re-installing Windows 7 Home Premium 65-bit last month?
Any further advice or suggestions would be greatly appreciated.
Many thanks.

The missing (incompletely displayed) information is the visual content within buttons and banners and sometimes the outlines of boxes, buttons, etc. I cannot see this content but when I hover over the empty button or banner with the cursor a floating menu appears which lists the contents (text only). I know that sometimes the content is symbols like arrows, etc. These never display on my system but I know what the contents should be by looking at the page with another computer. I have never been able to view the symbols on my system.
Thank you for your suggestion about using the Developer Tool in Windows IE. I followed your instructions using the F12 and Ctrl 4 keys to call up the Developer Network Tool.
Two items did not get a result of "200":
URL: file///about%7Cblank Result: (file)
URL: https://assets.annotateit.org/vendor...=1414960482918 Result: 0
I'm not sure what this means.
Should I delete these?
Is there an equivalent analysis for Firefox?
I appreciate your help.
Thanks.

I just accidentally ran the Developer "Network" Tool again. This time the results were different from the first time. In addition to the two items listed in my previous post, the following three items did not return a result of "200":

https://api.segment.io/v1/p HTTPS OPTIONS (Aborted) 275 B 3.13 s CORS Preflight 5414 530 2605 0 0 63493


https://api.segment.io/v1/i HTTPS OPTIONS (Aborted) 275 B 2.69 s CORS Preflight 5850 188 2511 0 0 63493


https://api.segment.io/v1/t HTTPS OPTIONS (Aborted) 275 B 3.12 s CORS Preflight 5429 577 2543 0 0 63493

I don't know what this means. Should I delete these items? Take some other action?
Thanks.

I ran the F12 key on Firefox. Under the category of "Console" two items were displayed with an orange triangle with an exclamation mark beside each:

mutating the [[Prototype]] of an object will cause your code to run very slowly; instead create the object with the correct initial [[Prototype]] value using Object.create lms-modules.eb701a7990a7.js:5

Use of getPreventDefault() is deprecated. Use defaultPrevented instead. 1743970571.js:92

I haven't a clue about what this may imply.
Is there action I can take?