Many sites show a "Back to top" link in their footer. Others, even worse, have that link throughout the page.
Personally, I never used any of them, but probably it's me to be strange.
Do you think it is an useful link?
UPDATE: when I rarely need to go straight back to the top I use CMD + upwards arrow
Well, some sites have fairly long pages, so why not. Yea, I use it sometimes if I clearly see it, otherwise I just scroll wheel up.
It's a BIG help for those who do not have a scroll wheel though, so I like it from an accessibility standpoint.
It is useful for longer pages and those who don't have easy ways to scroll up quickly (read scroll wheel), however if the page is exceedingly long and almost requires a "Back to Top" link, you should probably consider redoing that page to split it up.
So, useful, yes. Neccessary, almost always no. There are better ways to do it.
You should consider that some of your audience knows to hit the Home key to go to the top, some know to scroll and some barely can handle using a mouse. If the page is really long you might want to keep in mind that for some people, that is the best way to get back to the start.
On pages that have their only (or most-useful) navigation at the top of the page and have extremely long pages then 'to top' links are great. And for those users without scroll mice or other aids, such as mobile pages or screen readers (maybe).
From a usability stand-point, it can be helpful for people who rely on a screen-reader.
If you use it or not is of no relevance. Modern webpages (together with the browsers) offer many different ways to navigate a site. Which way you use is a highly individual thing. There are definitely users out there who will find it useful. So my answer is:
If your page has a lot of scrolling, you should seriously consider putting it in there.
I think much of the increase in this type of link has to do with mobile computing. Way easier to get back to the top of the page on a mobile device with a small screen and limited navigation capabilities using a "back to top" link. The same is true for people using accessibility applications to navigate the web.
Sites that have any cross-referencing content always do well to link directly to those cross-references.
If there is something interesting that happens to be at the top, great - but don't make "Top" a special section if it's not.
When it is necessary to have the link, I like when it is:
I don't think it's necessary to have "To Top" links sprinked throughout your page unless you are REALLY REALLY concerned about accessibility. (Even if the person is using a screen-reader... don't those things have a "start over" command?)
Think about web pages that have table of contents at the top that are links to other sections on the same page, I see a lot of FAQ, documentation, and help pages with this format. Not having a back to top link can be a painful user experience if your browsing from a device that does not have a 'Home' key, like your phone.
I think that for the sake of usability and utility, more than accesibility, you should put at least one link at the bottom when the scroll is long enough (with long enough I mean 3 or more screens down). I think if you read all the way down the article or content, then you might need a helping hand, but if the architecture of the site is well done, then hitting back may be better than home.
I'm against the middle page "go-to-top" cause you get a loop in your page that makes no sense unless you've inserted a top nav in the same page like a alphabetical hierarchy or a concept definition list, that obviously has a short lenght and it has nothing to do with the next one. That's the only situation when using the uplink will justify for itself, but I would try to avoid situations like that for the site architecture health.
An example could be this site. But again, it could be a "pita" trying to navigate this from a mobile, but just having the idea of doing it should be considered nonsense.
MHO