Temp directory not writeable by webserver

At most *inix/OS X system are you able to simply use /tmp

I also am getting this message! any one know how to resolve the issue?

Found a solution in another post

You need to go to, admin/settings/file-system
Then change Temporary directory:
From C:\xampp\tmp to /tmp

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Okay, so the solution seems to only apply to localhost. What about live servers? If I try and make the temporary file change location to "/tmp" in File system I get an error saying "/tmp does not exist".

So, I am assuming I have to create a "/tmp" folder on my server. Where should I put it? Within Imagecache folder? Where specifically?

Real servers already have a /tmp folder. Only IIS may have a problem with that.
As for where - /tmp begins with a / - that means it refers to the root of the filesystem.
For local dev that will also be portable, you can set it to sites/default/files/tmp . No leading slash.

My server is Linux based with a Plesk control panel. So in my case, "/tmp" should be okay as should "sites/default/files/tmp"?

Well I tried both "/tmp" and "\tmp" but it still states the folder doesn't exist. Do I need to create one? In my httpdoc folder?

Edit:::
I ended up just setting it to "sites/default/files". Seems to be okay. Its the same as my "permanent file" location. On a related note where should the "permanent files" be stored, not temporary files?

Edit 2:::
Oddly enough, when checking the status report page it still says Imagecache temp folder is still no writeable by the webserver, despite being able to save the path on File System.

"sites/default/files/imagecache is not writeable by the webserver"

I guess Imagecache appends "/imagecache" to the path. I've changed the folder permissions from 755 to 777.

After making the file permission changes on the Status Report page under File System it says "Writable (public download method)". Is this secure?

Thanks post #2 PenguinPie, that worked for me. I guess it's because it's Windows and the slashes go the other way. This fixed things and now no longer getting an issues. Wow, I spent so much time looking into permission issues and it was just an issue with the path incorrect for Windows when I came from having the production site on a linux machine. stupid, but happy I got it resolved. thanks again!

Thanks PenguinPie, It worked for me.