However after doing a bit of testing I see that this character is not used to represent missing glyphs on either my Windows 7 computer or the Android phone I've tested with (Motorola Atrix).

Different ways to prepend a line: (echo 'line to prepend';cat file)|sponge file sed -i '1iline to prepend' file # GNU sed -i '' $'1i\\\nline to prepend\n' file # BSD printf %s\\n 0a 'line to prepend' . w|ed -s file perl -pi -e 'print"line to prepend\n"if$.==1' file

all are basically standard SQL, but no RDBMS supports the standard completely.

With every other change I make, I have to test in a dozen clients and make sure it looks fine. Why is there so much variation in email style implementation amongst different clients?

I've worked with people at companies where this was their only responsibility. Setting up emails for clients, making sure they pass a battery of tests and look great in all browsers and clients. It's an incredible PITA and it's not a set it and forget it thing. Clients can change month to month; spam filters change, etc...

There is a lot of variation in styling support among different mail clients

Also cross-compatibility with mail clients can be hairy, so you should see what the industry experts are doing.

Email tools/clients are inconsistent in how they render HTML and CSS. A designed email might look great in Gmail, broken in Outlook, and unreadable in Apple Mail. Half of all emails are opened on mobile devices (according to one study). Email looks good in different clients? Great, now make it work on a 4" screen just as well as on a desktop.

For Mac OS X, the syntax seems to be:

Open About Popover

On Windows, wall time is measured using GetTickCount(), on MacOS by mach_absolute_time, on Linux by clock_gettime and otherwise by gettimeofday.