How to Speed Up Website Load Time
Website load time is a key factor in user satisfaction. If you speed up website load time, you get the added benefit of reducing shopping cart abandonment, increasing the amount of time people spend on your website, improving ad click-thru rates, as well as improved SEO with fast page loads. If you run an AdWords campaign directing traffic to your site, fast page load speed translates to a higher quality score in ranking for keywords in the bidding pool. The following tips will help you speed up website load time no matter which factors you're aiming for.
Reduce the number of HTTP requests
Optimize Image Files
Unless your website designer was specifically instructed to optimize theme images for page load speed, it's very likely many of your theme images are too big. You can solve this problem by using lossless image compression tools to re-compress the images. In some cases, converting the file to another format will also reduce the overall file size. Tools for both PNG and JPG files exist to quickly perform lossless compression. For uploaded files, like the ones included in web page body copy or blog posts, be sure the images are properly sized. I have seen many blog posts where the width and height attributes of an image are changed in the HTML, but the actual image is big. If you want a small version of the image to appear in the post, resize the image to the size you want, then upload the smaller version.
Serve Images from an External Domain
Gzip compression allows your server to compress HTML before it gets delivered to the browser. This reduces the file size and translates to a faster load time. Check with your webhost to see if this can be enabled. If your hosting provider doesn't support gzip compression, consider getting a new hosting provider.
Valid HTML loads more quickly in most browsers. If your web pages are full of HTML validation errors, you are forcing the browser rendering engine to work harder at figuring out what the page is supposed to look like. This means longer load times for the end user. Fixing those validation errors reduces the amount of time it takes for a web browser to render the page. Valid HTML may also have the added benefit of improving your page quality score in Google's ranking algorithm, which improves your chances of ranking higher in search engines.
Eliminate duplicate requests
Eliminating duplicate requests ties into the tip about reduced HTTP requests. WordPress plugins are notorious for calling jQuery independent of the built-in WordPress call to jQuery. I have seen many installs where jQuery is called three or more times, often requesting a separate file on the server each time. This is a waste of HTTP requests and a needless drain on page load speed. jQuery only needs to be called once per page. Bonus points for using Google's jQuery library, which increases the chances of a caching benfit from other sites also using it. jQuery isn't the only offender in the duplicate request category, it happens to be the most obvious one. Look for other places where duplication is occuring and squash those too.