Signing into a site that you have already registered with should be a smooth experience, but I've recently been frustrated by my own lack of foresight. I have three different email addresses that I use to sign up for various services on the web. I have a Yahoo address that I've had forever, a Gmail address, and my Six Apart address. Unfortunately, I haven't been as careful as I should have been about which address I use to register and I sometimes find myself having to try each of those addresses (and a couple of different passwords) in a frustrating attempt to login to sites that I visit relatively often.

This is a case where the assumption has been made that people know their email address (which is usually a pretty solid assumption), but in my case I've created friction for myself by not using the same email address every time.

It's my own fault, I know, but there is a way that sites can help me with this problem: tell me whether the email address is wrong or just the password is wrong. If the email address that I've entered exists on the system don't just give me the generic "Login is incorrect" message. The error messaging should state either "This email address does not exist on our system" OR "The password you have entered for this email address is incorrect." I know that would make my life a little easier.

"Designing for Flow" doesn't mean creating a challenging user experience. It's simply a recognition that web apps are becoming more and more complex and are helping accomplish tasks that require more time and effort. All sites that seek to help people perform complex tasks are capable of inspiring flow in users.

"Designing for Flow" just allows you to measure your site against four simple rules: does it set clear goals, provide immediate feedback, maximize efficiency and allow for discovery? You can make these assessments on a site-wide level or in reference to a specific task. However, it's not a replacement for proven usability techniques like those found in Don't Make Me Think or Designing Web Usability. "Designing for Flow" is a filter through which to view the design of your website.

If you're familiar with Basecamp or Backpack (both from 37signals), you know that when you sign up you're given a special URL to login to your account. It's usually something like "username.backpackit.com."

Let's say that you haven't used Backpack in a while and you go the homepage and find the login link (which is tiny and easily missed) but when you go to the Backpack login page, instead of a login form, you're given instructions about your login URL.

Personally, I've never liked this system. I don't use Basecamp or Backpack very often and always forget to bookmark my login URL and am always frustrated when I can't login from the login page.

Tonight I was trying out StikiPad and found that they give users a login url, but they also allow you to login right from their homepage.

I'm a big fan of 37signals, but on this point I think StikiPad does it better.

I've been using a wiki to do some documentation recently and I suddenly noticed that the search form has two buttons: "Go" and "Search." After a some experimenting, I realized that pressing the "Go" button takes you directly to a page named whatever you typed into the text input (/wiki/test) and pressing the "Search" button searches the wiki for that term. Even if the buttons serve two discreet functions, you have to admit this is hardly intuitive.