Everything about McMaster-Carr's site is built for speed and ease. I can literally have an idea, find the category, identify the specific part, and complete an order in about twenty seconds. (I've done this during a phone call. In the time it took my coworker to articulate the part he was looking for and finish his sentence, I was able to reply "It'll be here tomorrow.")
HomeDepot on the other hand sometimes takes 20 or 30 seconds to render the page to the point that I can see prices. I just checked with a page whose URL was already in my history, an unusually brisk 7 seconds. (Gag!) How do they screw it up so bad? I honestly don't understand how a web page can take so long to do anything.