2 main things you want to look at:
Do not format your text by selecting the font drop down list in the Text/HTML editor. - You need to set the formatting of the text within the skin.css file.
The reason for this is that if you use the font drop down list, it adds a ton of font tags to your code which means the file size of your pages is much larger than they need to be.
This is a common mistake that everyone makes when first using DNN.
You also do not want to paste content from Word, it looks as though some of the content in the Home page has been pasted from word
Check out this article for further info:
Bad practices when working with the Text HTML moduleThe next thing is to ensure your website loads quickly as it took a long time to load up for the first view. - I've written a post about this here:
DNN Performance enhancementsthanks,