Most (if not all) search engines are unable to index frames-based websites properly. Because frames are made up of multiple pages, only one frame is indexed at a time. It's not indexed within context of the other frames. This often means that, when someone finds your website via a search engine, your website looks wrong.
Frames are Not "URL Friendly"
With frames based websites, all pages share the same URL. For example, if your homepage is located at 'yoursite.com', when you click through to other pages on your website, the URL won't change.
This causes problems if someone tries to bookmark a page. If they click through to a subsequent page they find useful, they might want to bookmark it. Problem is, instead of bookmarking say, 'yoursite.com/about_us.html', they would be bookmarking 'yoursite.com' - the homepage!
Frames are Not as Accessible
Although most modern browsers support frames-based websites, not all do. It is for this reason that you should always implement a 'noframes' version of your website for user agents who are unable to view the frames-based version.
Disadvantages of Using Frames
Disadvantages(Cons) of using Frames :
1. One of the main disadvantage of frames is search engines will not deal with them properly. i.e, search engines (including most popular ones) will not index pages containing frames as its hard for them to search for a specific content and move backwards to check to which frameset each page belongs to and retrieve all the pages in the frameset.
2. Its hard to navigate through pages in frames when we have more than two or three frames.
3. Its difficult to print the content of all frames when compared to a normal web page.
4.. Some browsers doesn't support frames, so we need to place the content seperately for the people who doesn't have frames using noframes tags
5. We cannot bookmark individual pages using browser's Favourites Menu.
