First of all, I can't see that you have added the html according to the source example
https://www.w3schools.com/howto/howto_css_timeline.asp. This example clearly has elements with
containertime timeleft and
containertime timeright, with
timecontent element inside.
In your example, you just have elements
container left and
container right, not according to the example, and I can't see any
timecontent element inside either:
For this to work according to the example, it has to be done with the right elements and classes at least. Then, unless your custom class names are crashing with X3 class names, it should work. In your classes, you are using very general terms like
"container", "left" and "
right". Really, you should have class names that won't crash ... For example like in the original source
"containertime" and
"timeleft" are unique names, created specifically for the timeline design.
You also have a custom class for
"content" even, which is used by X3. That is why you are getting that white rectangle at the top. You need to use unique class names, and besides, I don't see where you get those styles and classnames from, because they are not in the example you are referring to.