Images, Graphics and Flash Animation
Many sites have images or graphics that are too large. By too large, I don't necessarily mean the dimensions of the images, but that the file size is excessive and it doesn't load quickly in a web browser. There are no hard and fast rules about file sizes, but if the website doesn't load in a few seconds most visitors will move on to a different website. Have a qualified web designer check out the website and make sure there isn't an abundance of large images that may slow down your website. You can reduce image size by reducing the quality, for instance with jpegs even a compressed image will still display fine for the web.
Another issue is Flash animation. While animation can add a nice dimension to your website, it can slow down the speed of your website, and sometimes just become tiresome if over used. Once your visitors have seen the animation a few times they probably won't want to wait each time while it plays again. Animation, if used sparingly and with taste, can enhance a website without bogging it down, but more and more websites that once had intro Flash pages are removing them. Excessive us of Flash can also decrease your search engine rankings.
Web Page Code
Check your code and make sure that it is efficient and well written. If you have any comments in your code then take these out. Just reducing the code bloat of your site can save a few Kb each time your page is accessed – and given a site gets thousands of hits a day, that can save you a lot of money in bandwidth charges.
CSS and Caching
Having your web page style information in an external file can improve performance since CSS style sheets are cached the first time they are accessed. Therefore when a visitor goes to different pages on your site, any CSS style sheets that have already been accessed will remain in cache. CSS is also a great way to limit the amount of HTML code by separating code from content. Any style information can be declared in one place, but used throughout your web site.
Links
Make sure any links in your web pages are valid. So if you link to other web pages on external websites, make sure that the pages still exist. Occasionally page names change on external sites, which can cause links to become invalid. This is also a detriment as far as search engines. Search engines check for links and if there are bad link, they may penalize your site. Of course links to internal pages on your site should be valid as well. So if you add and remove web pages on your site, insure that any links to these pages remain accurate.
Hosting
If your website is still slow after cleaning up your HTML code, trimming back the size of your images, graphics and animation, you may want to evaluate the quality of your web host. I don't recommend free hosting. You need reliability and accountability in regards to website hosting, and free hosting providers usually have servers that are overly taxed and lack the resources needed.
Design
Some websites are beautifully designed with lots of graphics, but if your visitors can't quickly and easily navigate your site, what's the point? Remember the goal of your website. Is it to sell a product or service, provide information, or is it to dazzle the visitor with animation and web design skills? I've found that most successful websites inform, provide an important message, or sell a product safely, securely and efficiently.