To save time and money when developing complex sites, frameworks like Drupal and Compass/SASS were invented. Before these frameworks existed, websites that relied heavily on content management, and custom made programming would require clients to have a humongous budget. Why? Because doing everything from scratch to code all of the different features would take hours and hours to implement, test, Q&A, debug and test again. A software program is only as good as the developer/tester who created it. But, if a program is only being tested by a few people, how trustworthy can it be?
Another website accelerator that caches MySQL queries, and PHP executions is called Memcache. Memcache decreases the load on the server, enabling you to deliver the pages to your end-users more quickly because it doesn't need to calculate queries from the database anymore, but fetches it from the memory cache instead.
To significantly speed up web applications, there is a HTTP web caching accelerator called Varnish. Its main point is to cache contents to speed up the delivery of web pages to its end users. The installation of Varnish may be troublesome, but here are the steps I use to get it working on my own server and for Drupal sites:
There are many open source frameworks that are released to make theming simpler. One of the problems that themers / front-end developers usually face is the amount of CSS3 features that many want to use, but not all of the different browsers has the capability of getting it working correctly. Therefore, CSS preprocessors like Compass and SASS makes this possible by having predefined mixins, variables, rules and inheritance that are similar to the concepts of Object Oriented Programming.
As a web developer, I've come across many different types of Content Management Systems (CMS for short). CMS is a web application that allows web publishers to easily manage their contents without the need to know how to code. It is the job of a web developer to make this possible for non-technical companies to have a professional looking website in order to gain more business.