[Animats]

"My password manager fills out the registration form, of course, but it won't submit because it wants an email address, not a username."

Big UI pain: sites that are not compatible with browser-stored login info.

[aptwebapps]

My bank just broke compatibility with my password manager (could be the plugin's fault, I suppose) and another financial institution specifically told me that their site was not compatible with password managers. They have this 'nifty' feature which turns all but the last few chars of your username into stars on blur and I suspect they just didn't want to bother to do their js event handlers properly. Fortunately, it turns out I can make it work with the right sequence of clicking inside and outside the input boxes.

[joelhumphrey]

Even though the login behavior on a web app's home page can cause hiccups with password manager compatibility, the alternate login form on the "You are now logged out" page is usually barebones enough to be compatible.

Compare the login forms for Verizon Wireless:

Home page - https://www.verizonwireless.com (upper right corner)

Logged out page - https://login.vzw.com/cdsso/public/c/logout

Tweaking your password manager settings to log you in through a site's logged out page can often bypass the compatibility headaches.

Using 1Password's Chrome extension, this trick has worked for me so far, although your mileage may vary.

[aptwebapps]

I used to use that method for the one that "didn't support password managers" before figuring out the click dance. Just tried with my main bank and they don't have a login form on the logout page.