At one of my previous jobs I worked on dozens of websites that had been created by other people. I prefer to use tabs instead of spaces when indenting code, and I can get a little OCD sometimes, so every time I edited a file I would do a search and replace to change every 4 spaces to a tab character. I didn’t like the idea of having some files use spaces while others used tabs, so when I wrote a bash script for recursively searching and replacing inside text files throughout an entire directory structure, I added some code that would clean up the white space as well. The actions it performed were:

• Converting from Windows (“\r\n”) or Mac (“\r” on older versions) end of line encodings to Unix style encodings (just “\n”)
• Removing trailing whitespace from the end of lines
• Condensing multiple blank lines to single blank lines
• And most importantly, converting every 4 spaces to a tab character

I had anticipated that this would save some disk space, but I was surprised by how much; after running the bash script, the total size of each website would decrease by 10-50% (that’s not a typo, fifty), and that’s including binary files such as images and PDFs which were unchanged. Think about the impact that has. Every individual whitespace character takes up 1 byte, bytes which have to be stored on disk, loaded into memory, transferred over a network, loaded into the client’s memory, and iterated past when it gets processed by the browser. Whitespace management saves:

• Disk Space
• RAM
• Processing Power
• Bandwidth

which in turn helps save:

• Money
• Electricity
• the Environment

It also helps you provide a better user experience. When browsing the Internet, I’d much rather download a 5KB HTML file than a 10KB one, since it’ll download faster and render faster.
(On a side note, generally these are all also benefits of writing standards compliant, semantic XHTML with external CSS and JS.)

Another reason I prefer tabs to spaces is, when browsing code it’s easier to tell if the proper levels of indentation are being used. If there’s one space missing or one additional space it can sometimes be hard to tell, but if a tab character is missing it’s very obvious. Also, most text editors allow you to specify how wide a tab character should be displayed, so if one developer likes 8 space indentation width, another likes 4 spaces, and another likes 2 spaces, they can all use the same code containing tabs and configure their respective editors to display the tab character at their preferred width. If you were to use 4 space characters for each indentation level, the developers who like 8 and 2 spaces are forced to use it as well.