2013 New information - We've started using fly out menus on several of our projects. several things have allowed us to do this with a light heart - there's better support for newer CSS's to get the same effect with less code bloat - and modern search engine robots now follow the menu options - as well as being able to use a Google Site Map to get pages into search engines. Browers support more options and web visitors know there is a standard way of interacting with move down menus.
This can also be called “Dynamic Menus” rather than “static” page html navigation links.
So that is one reason why they are a bad idea – they all work slightly differently as there is no “standard” way to implement them.
Some of the better ones have indicators when there are subsections available – but lots don’t – I’ve even clicked on what looks like the Main section heading without ever knowing that other pages were available under the option.
“The navigation got in the way of getting me to the information I wanted.”
With no “standard” in place for these you risk alienating your web visitor – and potentially the navigation may be getting in the way of that web visitor finding what he wants from the web site.
Web visitors come in all skill levels – you may have a web visitor to your web site that hasn’t seen many dynamic menus and they may not know how they work – their eye sight may be impaired and so the have the standard text size increased which again the fly out or move down menus often do not support.
There are two other main reasons why we don’t like Fly-out or Move Down Menus – speed and search engine optimisation.
I’ve seen pages that are huge in file size and take ages to download and ages again to then load & display in the browser – just because of the overhead of having to load and process the menu code. Not good…
I recall a survey that linked a web visitors “trust” and “accuracy” of information on a web page to the time it takes to load a page – the faster loading web pages / sites were judged to be more “trustworthy” – interesting indeed…!
A way around this is to have text links also on the pages – at the very least to a site map page or even a special page just created as search engine bait – but many of the web sites that use Fly out or Move Down menus do not have such a page.