Article in English: You can't update Safari on OS X 10.5 (Leopard) or earlier, so you'll need to upgrade to at least OS X 10.6, which means your Mac must have at least one gigabyte of RAM. You can verify this requirement by clicking the Apple icon in the top-left corner of the screen, clicking About This Mac, and looking at the number next to "Memory". You can buy a hard copy from Apple's store (http://www.apple.com/shop/product/MC573Z/A/mac-os-x-106-snow-leopard), or you can search for "Mac OS X Snow Leopard" on Amazon. Snow Leopard is the first rendition of OS X to run the Apple App Store, which is necessary to update to newer operating systems such as Yosemite or MacOS. You can also use the App Store to update Safari. To do so, insert the Snow Leopard CD into your Mac's CD slot (it's on the left side of the Mac's housing) and follow the on-screen instructions. You will have to restart your Mac during the installation process. It's an apple-shaped icon in the top-left corner of the screen. After a moment, you'll see a window pop up with several update options. You can elect to update to a newer version of OS X (e.g., Yosemite) from this window as well, though doing so will take some time. This button is in the bottom-right corner of the "Update" window. Doing so will install each item next to which you placed a checkmark. You may need to restart your computer during this process. Once the installation is complete, your Mac's version of Safari should be up-to-date for OS X 10.6, and you should no longer encounter error messages when attempting to access pages or software in Safari.

Summary in Vietnamese:
Bạn cần chắc rằng máy tính Mac của mình có thể chạy hệ điều hành OS X 10.6. Mua một bản sao hệ điều hành Mac OS X 10.6 (Snow Leopard). Cài đặt OS X 10.6 trên Macbook. Nhấp vào biểu tượng Apple Menu với hình quả táo, nằm ở góc trên bên trái màn hình. Nhấp vào Software Update (Cập nhật Phần mềm). Chắc rằng ô "Safari" được đánh dấu. Nhấp vào Install [con số] Items (Cài đặt số mục mà bạn chọn) ở góc dưới cùng, bên phải cửa sổ "Update" (Cập nhật). Chờ cho trình cập nhật hoàn tất việc cài đặt.