<i>This is the point where you realize that developers aren’t engineers, but craftsmen and that fixing these problems isn’t exactly a science but black voodoo magic.</i><p>I have mentioned it three or four times before but I'll say it again: the key takeaway from the YSlow presentations is that <i>fixing the frontend is a science, not black magic</i> and that <i>user-perceptible load times are dominated by front-end factors</i>.<p>Not your database! Not your application logic! Not your web framework! Not your idiom for string concatenation!<p>If you have three CSS files, condensing them to 1 CSS file is as close to zero technical risk as any intervention in the history of engineering, will take you far under a man-day to implement a process to correct this defect, and will provide instant, lasting, guaranteed performance gains everywhere you were using those three files.<p>If you don't gzip your Javascript, CSS, and HTML yet...<p>If you have spent weeks thinking about how to use memcached and not so much as a minute discussing expires headers...