Optimal interface for specifying a mapping between known field set and fields discovered in CSV file?

We are building a data import feature in which our users will open an arbitrary CSV file and define a one-to-one mapping of its fields to a list of known fields in our database. The list of fields is very long (around 30 know…
What is the name of this combined button/popupbutton?

This button is in the new Firefox, but what is the name of it?
What is the name of this combined button/popupbutton?

This button is in the new Firefox, but what is the name of it?
In which cases does it make sense to use an explanatory video on a homepage?

I am a junior designer and I working on a web service’s site design. I am not sure what should I place at the homepage i.e.:
Some services like dropbox and readability have a quick video tour which explains what the product …
In which cases does it make sense to use an explanatory video on a homepage?

I am a junior designer and I working on a web service’s site design. I am not sure what should I place at the homepage i.e.:
Some services like dropbox and readability have a quick video tour which explains what the product …
Font Size For Mobile Sites?

I am designing a mobile site, and I’m wondering what I should set the font size as. Any suggestions?
How do I restructure content to be more user friendly?

I’ve got a content management system that isn’t the most usable at the moment, but it is pretty intuitive for the end user. The front facing content is a mess, however, and someone decided that most of the pages should be sty…
Should double click be avoided in web applications?

I find that double click is a great gesture that could be successfully used in graphical interfaces but for some reason has negative connotation on the web. Should it be avoided at all costs?