Photoshop was made with Printer and physical media in mind. Lo and behold it is also the web protege. They keep both in mind in most cases, but alas not for all.
I am wondering if there is a way to make Photoshop default to pixel format over inches, as I consistently make changes in pixels and it saves me a ton of time if I do not have to hit width in PIXELS from inches over and over and over. I have fiddled with it on various occasions and can not get it to behave. For some reason they always go back as well instead of, like most programs, keeping the last or most picked option.
For instance I go to image width or canvas size to alter it first I have to change to pixels. I have NEVER used inches in my entire life and this is getting very old after over 6 years. Anyone got or know of a solution? I asked designers before and they are like SHRUG. To which I answer in tears, "WHY god why". ;_;
The trick with Adobe defaults is to set them with no document open. Otherwise the settings will apply to the current document. So, close all Photoshop documents and then set the Preferences > Units & Rulers Pane as Divya mentions.
Click on Preferences->Units & Rules to change the units to default to pixels. I have never had to fiddle with it after changing that.
Well for me, Photoshop does always remember the last-selected units (I normally use pixels, but occasionally change to mm). It might possibly be related to the "remember palette locations" option (I have it on), otherwise the problem might be that you are running without the right permissions for the appdata folder where Photoshop needs to store its settings (you don't mention your OS).
If you enabled the ruler, simply double-click the ruler, select pixel and thats it, i never had to change the options again. But also make sure that you have the permissions to save your configuration.
Do you know, why adobe Apps don't use your last, or most used function? Cause Adobe SUCKS terribly in usability! I suggest you to try Piexelmator if you can live without the print functionality.