Bottom right corner resize controls trump vertical scroll button if set to appear in the bottom corner

Question

My bottom right corner square of the Firefox window normally sits below the bottom of the vertical scroll bar and right of the horizontal scroll bar if one exists. The square is used to click and drag to resize the window's right and bottom boundaries.
At issue is when a web site places its vertical scroll down-arrow button in the bottom right corner. I cannot access the down-arrow button with my mouse to cause the page to scroll down a few lines at a time because when I point the mouse there, I get the resize controls instead. Even though the down-arrow button is plainly visible on the screen, the resize controls take charge and I cannot use the scroll control.
Two example web sites display their down-arrow control at the very bottom of the window; TIME.com and GMAIL.com. I have also viewed two PDF documents in the browser, and they too, have a vertical scroll bar all the way to the bottom, and I cannot use that down-arrow button because instead I get the northwest-southeast click-to-resize cursor instead of the mouse pointer when I attempt to use that button for scrolling.
Someone on the Google Help forum was not able to replicate that issue, showing me screenshots of his lower right corner mouse behavior. He does not have the resize control covering access to the scroll bar.
I am using the latest Firefox, I have reset Firefox, thus dumping all of my add-ons and custom settings, and have only put back AdBlock Plus and Cookie Monster. And Troubleshooter, when I asked a similar question.
I am running Windows XP, on its last days of support. This computer is not capable of running anything newer, unless I run with Linux.
Going to TIME.com, its vertical scroll is in the bottom corner and I get the resize control arrows instead of the mouse pointer when I point to the down-button. If I disable page styles in the View menu, I get a useful output that sets the end of the vertical scroll above the bottom corner. So somebody's idea of styling the page (CSS) creates this issue for me.
Going to Gmail, turning off the styles gives me a useless output of nonsense, so I must use page styling enabled.
Can someone please give me some guidance? This forum page has vertical and horizontal scroll above and left of the bottom corner square. I have access to all the parts of both scroll bars, as is the case on most well-designed pages.
My window-resize controls are in charge always of the bottom corner square even if the vertical scroll is supposed to be there.
See also my first wording of this question: https://support.mozilla.org/en-US/questions/993519

Answer 1

Those layout.css prefs are about enabling some CSS feature, in this case vertical writing, so have nothing to do with scroll bars.
*Bug 772321 - implement CSS parsing of writing-mode property
*resource://gre/greprefs.js
<pre><nowiki>// Is support for CSS vertical text enabled?
pref("layout.css.vertical-text.enabled", false); </nowiki></pre>
Can you attach a screenshot?
*http://en.wikipedia.org/wiki/Screenshot
*https://support.mozilla.org/kb/how-do-i-create-screenshot-my-problem
Use a compressed image type like PNG or JPG to save the screenshot.