The CSSOM (Cascading Style Sheets Object Model) is the browser's runtime representation of all the CSS applied to a page. It contains the styling rules that determine how elements should appear, including properties such as colour, size, visibility, layout, and positioning. The browser combines the CSSOM with the DOM to build the Render Tree, which is used to paint the page on screen.
For software testers, the CSSOM explains why an element can exist in the DOM but still be invisible or impossible to interact with. Properties such as display: none, visibility: hidden, opacity: 0, or pointer-events: none affect how elements behave without changing the DOM structure. Understanding the CSSOM helps diagnose automation failures where an element is present but not visible or clickable.
For software testers, the CSSOM explains why an element can exist in the DOM but still be invisible or impossible to interact with. Properties such as display: none, visibility: hidden, opacity: 0, or pointer-events: none affect how elements behave without changing the DOM structure. Understanding the CSSOM helps diagnose automation failures where an element is present but not visible or clickable.
