The Need for Speed
Site speed is obviously an important part of a website's success or failure. While you may be willing to sacrifice speed for a neat effect or feature think about yourself as the user. When was the last time you waited for a website to load and then thought "that was slow but (insert feature name) was really cool and worth the wait". Never.
The hard reality is that sometimes we get overly obsessed about "cool" and lose site of usability. And at the end of the day usability is what matters most because that effects whether visitors return or not.
The statistics on speed and it's affect on user behavior is nothing new. According to Kissmetrics 47% of users expect a site to load in 2 seconds or less and 40% abandon sites that take longer than 3 seconds to load. It took you longer to read those 2 sentences.
In 2016 Google officially announced it would start using mobile page speed in its ranking algorythm. This means that as of now a slow site is going to start hitting you in the search results.
Slow can be a subjective term but thanks to Google PageSpeed it's super easy to measure and get some insight into improvements you can (and should) make. You simply enter your URL in and Google will scan the page and measure load times. When it's done it gives you a score (0-100) and a list of issues it found. The issues are weighted so you'll know what is most important. It's worth noting that getting a score of 100 isn't the goal. I've never seen a site with a perfect score. You have to balance speed with function to get the best of both.
What to Do
Let's talk about what the top three "speed killers" are and how you can fix or reduce them.
1. Image Size
The most consistent speed issue is overly-large images. Bigger images equal bigger file sizes. When browsers are forced to fetch large images and downsize them for display you're spending time retrieving "pixels" that never get seen.
To fix this browse your key pages and determine the rendered image size. Then resize your images to that size and replace the large one. While you're at it play with the image quality settings to further reduce the file size. I find that for most JPG images I can save at 80% quality without noticeable effect. If you're using really nice stock photography or professional photography make sure you're saving it for web use (which further optimizes the filesize).
The solution for this is to minimize the number of connections needed for CSS and JS and defer their loading as much as possible. Admittedly it's quite difficult to completely eliminate this "issue" but it's impact can be greatly reduced. In most cases you'll need to involve your web developer to help work through this but it's worth the investment - especially if Google PageSpeed gave you more than 2 or 3 offending resources.
Most sites can enable caching in their .htaccess file. The .htaccess file controls a lot of what happens with your website so beware if you decide to edit it yourself. One wrong item and your site will fail to load.
If you decide to add caching to your .htaccess file here's an example of what a simple caching solution might look like.