Observation I'm unsure if accurate, but I've experienced firsthand: **It appears that the slider component of the scroll bar does not create/send "OnDrag" info until the cursor passes the midpoint of the slider. Thus, if I'm interested in scrolling down, for example, and I attempt to drag the control down, it won't respond until I'm half way down the component.** This obviously means that my page won't start scrolling initially, and then it will jump, rather than smoothly scrolling. In other tests I've done, I haven't seen the delay. For example, on a page that does not require a lot of scrolling, the slider is larger, and it seems responsive from the initial click point --- not just after the 50% point is hit. Because my tests are not displaying the same behavior, I may be off base... However... I have produced an MP4 of me slowly dragging the slider up and down a longer page, and periodically I'll be able to have the mouse pointer leave the slider (even though I'm still in a MouseDown state), and later the slider will catch-up to the pointer. I can e-mail the file to you, if you want it. There is additionally a lag in typing this post. As a test, I typed in the alphabet, and each character displayed instantaneously. But after a little while, about 10 characters buffered, and then all spilled out simultaneously. I wondered if it was my system, so I tried the test in Notepad, and it was fully responsive to each keystroke. (In typing the last sentence, the phrase "wondered if it was my system" all got buffered and sent to my textbox simultaneously.) Clearly, if there's an issue with typing text, it'll likely spill over to the responsiveness of other controls. Maybe the scrollbar and textboxes are fine, but there's a bigger issue hitting FireFox internally?