Could someone please explain what is the disadvantages using iframes for the side menu? I just plan to use it for the side menu in my site
I think for a basic website, frame and iframe are okay. Most of the browsers today support them so they are rarely broken now. But your site will have a lot of trouble with the search engines if you use frames. Just imagine a search engine found and indexed one of the page in your site, but when people click on the link, it takes you right to the page that's only in the frame... without your side menu or anything.