Borders disappear in Chrome when I zoom in

You are forcing Chrome to do subpixel calculation, and this usually has strange behaviours.

If you change the height of the input to 30px, then a 90% zoom works ok (because this is 27px), but a zoom of 75% not (because this is 22.50 px).

You can also avoid this by giving the border a width of 3px. In this case, you will see that the borders width is different in different places .

Anyway, the very best solution is to give more space around the inputs so that the border can be drawn cleanly even if it is in a subpixel position.

I'm pretty sure that Luís Pureza has solved his issue, but I found a really easy way to solve it changing only this:

If you have a table border like this one:

INPUT,TEXTAREA {
border-top: 1px solid #aaa
}

Change it to this one:

INPUT,TEXTAREA {
border-top: thin solid #aaa
}

I found this solution across this link: https://productforums.google.com/forum/#!topic/chrome/r1neUxqo5Gc

I hope it helps