Tutorial :Daunting task of refactoring 5000 line CSS. Any tips?


I've just been assigned the task to refactor a huge 5000 line CSS file... but here's the worst part - I also need to make it IE6 compatible. Any CSS gurus have suggestions of tools, or possibly tips (common pitfalls) for use in my monolithic expedition? Cheers.


checkout sass... it includes the ability to convert css to sass. http://haml.hamptoncatlin.com/docs/rdoc/classes/Sass.html

A sass file is a yaml file that can be parsed down into a css file. It allows you to use variables and alternate organization...

sass example:

  !main_color = #00ff00      #main      :color = !main_color      :p        :background-color = !main_color        :color #000000  

css output:

  #main {      color: #00ff00; }      #main p {        background-color: #00ff00;        color: #000000; }  


Some tips:

  1. Use version control so you can roll back when needed.
  2. Come up with a checklist of visual tests to run through after each change, in each browser. A spreadsheet of URL links and things to look for, building on them as you run across problems (think "unit tests" but not automated).
  3. Use a CSS-specific beautifier first to get everything into the format you prefer for braces, etc.
  4. Consider using something like SASS to "compile" your CSS as you go along.
  5. Comment the heck out of things, especially where you're doing IE6-specific stuff.
  6. Future-proof yourself by building a separate file with IE6-specific directives as you go along, or at least use Microsoft's way of filtering them out for other browsers.
  7. Use the W3C Validation often.

Mechanically, I would attack it like this:

<link type="text/css" href="newhotness.css" />  <link type="text/css" href="newhotness-ie6.css" />  <link type="text/css" href="oldandbusted.css" />  

Move code from the third (old) file into the other two, cleaning up as you go. That way you can validate your code without worrying about tons of errors in the old stuff, and you can track your progress, Ctrl-Tab between them more easily than between locations in a single file, etc.

(If you can't control the markup to add your CSS files, use an @import at the top of the old file.)


Start from scratch!

Assuming you can check all the major pages manually, I would be VERY tempted to wipe the entire file and start from scratch. Spot-checking for IE6 inconsistencies, you'll be doing nearly the same amount of work anyway, but it will be much, much more painful if you're modifying old, browser-specific CSS.

That 5000 lines may well be expressable in 2000 lines of modern, well-designed CSS. I think most experienced CSS developers would find it less work to write 2k lines of new CSS than modify 5k lines of horrible CSS.



which is based on this:



Not necessarily CSS, but here's worflow tip: use GIT.

  • start off by importing the files in git;
  • commit for every minor step, and record what you did;
  • whenever you find that you broke something, you can identify the exact same step broke using git bisect ( a good description );

For extra kicks, here's a talk about code coverage for CSS to help you quickly weed out unused rules.


As Triptych said, I would start from scratch. Also, consider the following:

  • use a CSS reset file to smooth out cross-browser inconsistencies: http://meyerweb.com/eric/thoughts/2007/05/01/reset-reloaded/
  • get it working perfectly in Firefox, then tweak for other browsers as needed
  • study the underlying HTML. How is it organized? Is it laid out with tables? all DIVs? Semantic tagging?
  • is the CSS used for layout or simply styling (fonts, colors, etc.)?
  • Once you get a feel for that, study the content. Categorize the layout and elements as much as possible, so that you identify all the common elements and can maximize the efficiency of your CSS
  • remember the C in CSS, Make the most commonly used font the body font, so that other elements will inherit it by default.
  • use relative units (ems) for font size, to allow proper scaling of text
  • try not to use ANY inline styles
  • make use of Firebug - it will let you inspect an element and see exactly what CSS is in effect and where the rules came from
  • don't be afraid to re-use portions of the old CSS, especially for things like dropdown menus, which can need very specific incantations to work properly
  • have fun! starting from scratch lets you implement best practices and learn a ton along the way. When you are done you are probably going to look back on this as a good experience.
  • there is a presentation here that should get you in the right headspace for tackling this task: CSS Systems


I would be tempted into creating a test suite first: automating page visits (perhaps with Selenium?), taking screenshots, then using something like ImageMagick to compare those with reference images.

Also, I second all the suggestions to use source control. If you later discover that your refactorings broke something that wasn't checked by the test suite, you can add a new test and then bisect your history to find the change that broke it. Git is good for that.


Get a code editor with good syntax highlighting. Also, goodluck I dont envy you.


My initial thought was does some like NCover exist for CSS, as it would be handy to see if all of the CSS is referenced. A quick Google on CSS code coverage found a few things- you might want to look yourself though: http://development.lombardi.com/?p=436


Install sass, run css2sass on your 5000 lines of css, proceed. After you are done with your sass file refactoring, run sass2css to regenerate the css file. Best of luck!


I'd suggest Stylizer - it is a CSS editor with an embedded live preview browser. It makes life much easier when editing CSS files and can tell you which rules affect which element on the page and more.


All of you guys saying he should start from scratch are wrong. You shouldn't. Try to identify the different parts the site uses. Put them on a sheet of paper. Find the parts that match together. Build a structure. Find parts of the application that are the same but are still styled with different rules.

Take that one part and name it. Then match all app parts that use that "pattern" with the correct HTML/CSS.

Repeat until you're done. Break up the large task in small chunks.

Identify whether the original CSS writer used standard methods like using a CSS reset. If he didn't, and everything is defined by #id without reusable classes, well, then maybe the guys saying you should start from scratch are in fact right. But my point here is that you can't just recommend that without assessing the situation.


Using the Dust-Me Selectors Firefox Plugin can be handy. It's a bit like a code coverage tool for CSS.


Tool suggestion: ReSharper by JetBrains. It will autocomplete CSS and rename selectors site wide from the CSS file editing window.

Note:If u also have question or solution just comment us below or mail us on toontricks1994@gmail.com
Next Post »