3. Don’t Resize Images within HTML : Donot upload large images to the page and then place width and height tags for that image to make it look small. Just upload the exact dimensions of the image file.
4. Specify Image Dimensions : While placing images on your webpage, make sure, you have defined the width and height tags to the image html tag. It makes the search engines and the browser to understand the image behavior easily and quickly.
5. Use CSS Sprites for images : If your website page has a lot of times, it takes more time for the browser to render all those files. In order to make it easier for the browser , try using CSS sprites and getting all of your common image files into one single image , which is called a sprite.
6. Optimize the Joomla Template : Always have the best and latest coding standards applied to your Joomla template. Avoid using any framework which loads a lot of script files. You finally end up with a slow website.
7. Update your Joomla Extensions : Always stay updated to the latest Joomla core package and all the extensions to avoid any conflicts.
8. Use Joomla Cache : Switch on Joomla Cache plugin and also at Global Configuration. It works pretty well.
9. Convert from Table to CSS based layout : Donot code the Joomla template in html tables. Always use div based coding only.
10. Use External Style Sheets : Host your CSS files on a CDN network.
12. Remove Unnecessary White Space in template files : Dont have any white space on your Joomla template php files.
13. Use responsive CSS : Use responsive framework like Twitter Bootstrap. The enhanced css coding helps with the website loading issues.
14. On Page Optimization : After you are done with the website, always make sure, you check the website on various tools to do its on page optimization.
15. Specify the DocType in the Joomla Template index.php : Pages that have the DocType specified tend to load faster than those that don’t.
16. Reduce HTTP requests : Keep an eye on the external HTTP requests. It one of the most important factor, that affects the website speed.
17. Use Gzip Compression : Enable it on your Joomla Global Configuration
18. Avoid too much Joomla Extensions : Only use the extensions, which you really need to. Donot install any extra extensions as it adds to the resource usage and thereby affects the speed.
19. Use SSD based hosting : 99% of websites currently are on HDD based hosting servers. The bets bet to get an immediate boost is getting a SSD based hosting. As far as I know, LiquidWeb provides the best SSD based plans. You can see your website loading like a rocket with a SSD.
20. Better Server RAM : For a basic website with basic traffic, you should be fine with a 512MB RAM too. But if you are targeting a lot of customers and getting good traffic, make sure, you request your host to upgrade your server to a better RAM like 1GB or 2GB or may be more, depending on your traffic stats.
21. Reduce Size & Number of Cookies : Be careful about the total number of cookie requests and their size. They also affect the website speed.
22. Use CDN Networks : Apart from the web hosting, a good CDN service is must for any website. CDN helps to load all the website asset files in a quick time by caching those files on their nearest cloud server.
23. Avoid too many plugins usage : Plan the plugins, which you really need. Keeping more number of plugins active, it starts to laod on each page load and affects speed.
24. Use CSS & JS Compression : Apart from Joomla GZIP, its a good practice to use some CSS and JS compression joomla plugin.
25. Avoid using 3rd party brigdes : If you looking for some core integration with an external script or software, I would recommend staying away from any kind of brigdes, unless someone really offers an optimized bridge application, which has been fully tested, etc.