Win 10Pro 64, gigabyte socket 1156 mobo, 24g RAM, GeForce 710 nVidia graphics, Sandisk SSD C drive

My computer's old but continual upgrades have kept it going for more than ten years. I noticed recently that when I changed my graphics choices in browsers from white to a dark grey,the computer slowed way down. I like the darker color and don't want to return to the eye-throbbing white backdrops. The question is this: can it be my graphics card that's the bottleneck? The Geforce 710 is an $80 card. If I replace it with an upgrade will I get some speed benefits? Or is it just an aging computer? Thanks in advance, you guys always have the answers.

Arthur