The Golden Ratio is closely related to both the Fibonacci Sequence, and a ratio of 1:1:61. It can be found in nature, architecture, and art. Using the Golden Ratio is a helpful tool for designers to implement both attractive and functional sites that help guide the user in a natural way. An easy way to think about the Golden Ratio when designing, is to remember the Rule of Thirds - dividing the area equally into three sections both vertically and horizontally. You can then sub-divide these sections into further equal sections.
Being mindful of equal proportioning does not mean that as designers, we are held to symmetrical designs as the end-all-be-all of site design. Asymmetrical design can be challenging to implement, but working with balance and movement, and emphasizing motion and color, can make asymmetrical layouts visually appealing. The grid will still need to be in play - if anything, grids will be even more of use to the designer when working with asymmetrical layouts.
Layouts that violate principles of good design are numerous on the web - just search for "examples of ineffective layout design" and you'll receive several hundred hits with listicles extolling the menace of bad design. If you were a user of the web in the 90s, you probably remember the unspoken principle of web design that seemed to state, "If it can be added, add it." Flashing site titles, moving text and images, strobe-like effects, and busy, loud backgrounds underneath busy, loud content seemed to be the norm. For the good of all, we have evolved beyond those times. Continuing to use the Golden Ratio and grids can help us continuing to evolve toward better user experience on the web.