Pros of Using a CSS Framework
1. Speeds up your development:
A CSS framework lays out the groundwork for you so you can start developing quicker. It does that by giving you code for repetitive and common tasks—like resets—so you don’t need to write from scratch every time. And if you’re working with a team or collaborating with other developers, you all will have the same shared CSS code, so collaborative efforts are sped up as well.
2. Enables cross-browser functionality:
Remember the hair-pulling frustration of having to constantly tweak your CSS code so that your website or web app looks similar on all browsers? Well, you can say goodbye to that annoyance by using a CSS framework, which takes care of that for you. It’s already coded to look similar across all browser, so you can focus on customizing and creating content rather than tweaking the base appearance. A CSS framework will also eliminate browser-specific bugs, which is a nice plus.
3. Gives you clean and symmetrical layouts:
A grid-based CSS framework sets up a multi-column arrangement with predefined pixel widths so you can focus on creating content rather than lining up blocks of text. No more tweaking the pixel widths of columns to make sure they line up, or wondering if your sidebar width is standards-compliant for widgets or images, or any other annoyances that comes from guessing or figuring out what width you need to make your columns.
4. Enforces good web design habits:
A CSS framework enforces good habits like including a print stylesheet. It also gives you a set of selectors that you’ll use for all websites and web apps that you develop with the framework, which creates consistency in your web design. You don’t have to guess or remember what you did for one site or another – it’s all consistent.
Answer source: Pros and Cons of Using a CSS Framework