One of my major gripes is Illustrator’s inability to save and load preferences from within the program. This would come in handy when working in different units, as I regularly do; The 10px grid I use for web work isn’t compatible with an imperial or metric grid for print work, and vice versa. Luckily, I’ve devised a workaround.

1. First, you’ll need to find your Ai preferences file. For Windows 7, it can be found in a hidden folder:C:\Users\Username\AppData\Roaming\Adobe\Adobe Illustrator CS4 Settings\en_USFrom your explorer window, drag the en_US folder to your start menu and Pin it there. In OS X, you can similarly make a link to the folder and keep it in your Dock, desktop, or wherever you fancy. The file we’ll be renaming later is named AIPrefs (no extension)- we’ll deal with that soon enough. If you don’t have hidden folders visible, here’s how. If you’re on a different OS, or using a different version of Illustrator, have a look here, or search the nets.
2. Open Illustrator, start a blank document, and set your preferences. The document type doesn’t matter.
3. Close Illustrator.
4. Open the folder you linked in step 1, copy and rename your preferences file to something descriptive like AIPrefs[web]. It’s crucial to copy so we don’t accidentally modify or delete our manually defined preferences.
5. Repeat steps 2-4 for each grid-setup or preferences variation you need.
6. Now you’re ready to use your custom preferences. Before you reopen Illustrator, delete the current AIPrefs file.
7. Copy the preferences file you want to use and rename it to AIPrefs.
8. Start Illustrator and behold the glory.

Obviously, if the last thing you worked on is for web, and the current thing you worked on is for web, you don’t have to change the AIPrefs file, so it might be helpful to keep a note of which file is currently active. You can also search the AIPrefs file to see how Illustrator is modifying the contents. It’s for the most part readable alpha-numeric content. If anyone knows of a better way to do this, please let me know. Ciao.