Well, robots.txt prevent crawling and meta robots tag in HTML (or) X-Robots-Tag HTTP header prevents indexing (and other functionalities available too).  So, even when a URL is disallowed in robots.txt, it can be indexed in Google if it is referenced somewhere using an anchor tag.  So, my question is, how can I prevent public CDN URL being indexed by Google?  For example, I upload an image on Facebook which is private. But, the CDN URL holding the data is actually public, so anyone with the complete link can access the content. How does Facebook prevent these URLs being indexed?  Example textual URL:   Now, I posted the above URL here. Will google index this URL? Update:  How about this anchor URL: .  Will this be indexed if this is referenced this way?  Update:  When I say "link indexing", I'm not talking about  but .   Example:  in the site's  but you can see that it is actually indexed.  My question is, how does Facebook prevent the FBCDN URL above being indexed while you search like this in Google: site:fbcdn.net inurl:21616414_867163746798211_8462429064810946636_n.jpg  This didn't work, and my question is how does Facebook do this.  Reference 1:   Reference 2:   Reference 3:  (Check the table at bottom)
I use a cookieless sub domain static.example.com to serve all images, js, and css files. This static sub domain has as its root directory the same directory as the parent http://example.com. So static.example.com/index.php will result in calling the same file as http://example.com/index.php  Google has taken up indexing static.example.com and I need to stop this.  I can't modify robots.txt since it would apply to both domains. Webmaster tools allows "temporary" removal of a link, but this needs to be permanent.  I registered this static domain through google as a separate site from example.com, but this doesn't seem to buy me anything since I can't see a way to block crawling without using robots.txt - which would block it from the parent domain.  Any other ideas?  UPDATE  Found this conversation on   I am looking into whether it's possible to insert a META tag dynamically into the header of every page called on the static domain using php  CLARIFICATION  I am not putting any content on static.domain.com. There are NO webpages on it that are called - it only serves images. I have it redirecting to the same root directory as the main site for ease of coding image links (not every image is fed from the same image path).  Google got a hold of the static web root address - probably because .htaccess redirects to index.php if a file is missing and then crawled it. Now Google is showing the static version of the same pages with search results.
Why three-phase power? Why not a higher number of phases? Is there a reason, beyond historical reasons, that three phases has become the dominant number of phases?  I am aware of the advantages against one phase and two phase, namely the reduced amount of conductor needed, and that motors can provide torque when stalled (and less pulsation).  Is this solely due to diminishing returns, with only a small increase in smoothness of torque application, at the cost of increased complexity (increased number of wires (albeit of smaller CSA)).  To be clear, the phases are all evenly distributed, that is, five phases separated by 72 degrees. Making extra parameters optional I've setup a very specific function and it works well but I'd like to make the parameters optional but I can't get a handle on the regex bit:  add_rewrite_rule('whats-on/([^/]+)/([^/]+)/([^/]+)/?$', 'index.php?page_id=71&amp;event_year=$matches[1]&amp;event_month=$matches[2]&amp;event_day=$matches[3]','top');   /whats-on/2012/01/25 I'll show all events on this date.  /whats-on/2012/01 goes to 404 but I'd like the parameter to be optional so I can show all January dates and the same for /whats-on/2012 all dates in year 2012  Any help will gratefully received - thanks How do the review limits work? I got the brand new Custodian badge today for reviewing posts. Inspired by that, I reviewed some more suggested edits. Now I ran into a limit:     You have no more suggested edit votes today; come back in x hours.   How is that limit calculated? I made 61 reviews today which seems to be some calculated limit.  I searched for an answer on meta but found nothing helpful. How to change color of the text in TextView on hover like in css? How to add new element to Varargs? If $f(x + y) = f(x) + f(y)$ showing that $f(cx) = cf(x)$ holds for rational $c$ For $f:\mathbb{R}^n \to \mathbb{R}^m$, if $f(x + y) = f(x) + f(y)$ for then for rational $c$, how would you show that $f(cx) = cf(x)$ holds?  I tried that for $c = \frac{a}{b}$, $a,b \in \mathbb{Z}$ clearly  $$ f\left(\frac{a}{b}x\right) = f\left(\frac{x}{b}+\dots+\frac{x}{b}\right) = af\left(\frac{x}{b}\right) $$ but I can't seem to finish it, any help? How can the backtick character ` be included in code? I tried before to post a shell script that contained a ` character as an answer on Stack Overflow. The parser insisted on treating the backtick as formatting instead of part of code.  How can I include it? Use "does" in front of another verb in a question? What time does sound good to you?     What time sounds good to you?    Is there a difference? How to log out of a Stack Exchange site? Per the title, where is the logout button?  All the existing questions I can find refer to the previous design of the site, where hovering over your name in the top bar brought up a menu. Changing plurality in parentheses If a set of parentheses lies between a subject and its verb, and the parentheses contain an substitutive subject whose singularity/plurality disagrees with the original subject, whose singularity/plurality should be chosen for the verb?  In other words, in the following example, should "questions" (and its verb "are") be singular, or should they remain plural as shown?     Many (if not every) questions on this StackExchange are answered.   My intuition tells me that the two words in question should remain in plural forms, since the text in parentheses only interrupts the sentence (and the sentence would be grammatically incorrect if everything in parentheses were removed and the words were in singular form).  On the other hand, when read aloud (assuming one reads the text in parentheses), this has an uncomfortable sound to it, and I've seen others write in what would be the above example's singular-form case, so I'm curious to find out which is correct.  And, thinking about it, I suppose the same question would apply when commas are used in place of parentheses. I'm writing a script and I would like to pass the results from bc into a variable. I've declared 2 variables (var1 and var2) and have given them values.  In my script I want to pass the results from bc into another variable say var3 so that I can work with var3 for other calculations.  So far I have been able write the result to a file which is not what I'm looking for and also I've been able to echo the result in the terminal but I just want to pass the result to a variable at moment so that I can work with that variable.  echo "scale=2;$var1/var2" | bc How many ounces is a British "tin" of tomatoes? If I have a British recipe that lists "1 tin chopped plum tomatoes," how many ounces is that? In British English, does "tin" usually refer to a specific size? In the US, cans generally come in 14 and 28oz sizes - which one is likely closest to what the recipe means? How to change the hostname of a RHEL-based distro? Google Drive storage mismatch Hi all im a noob on Ubuntu/Linux World,  So i need some that give a full tutorial to How to install  from apachefriends.org correctly on Ubuntu 11.10 + all beyond Ubuntu for 32 bit and also 64 bit Desktop Version.. and also i need this:   Make a Folder on Your Home Folder and Linked to htdocs from Apache Web Server Make a GUI interface for Xmapp Start Xampp when Ubuntu Boot Up or Start Ubuntu   (Note: i ask it for both X86 and X64 so people in the further can see the tutorials)    New Data:  What i did was i download from  for now and i also what to say that I'm currently running Ubuntu 11.10 X64 bit for Dell Studio 1558 processor intel i3  i will let you know guys which solution was the best, and it is for a Desktop Version of Ubuntu 11.10 (Laptop 15 inch screen ^_^ ) not Server Ubuntu State of the art in quantum memory Presently, how much information can a quantum computer store, in how many qubits? What restrictions are there and how does it vary across realizations (efficiency of data storage, ease of reading and writing, etc)? Why does adding a curve modifier move my object to the center of the curve? I'm using a curve modifier and an array modifier. My object is at one end of the curve but as soon as I choose the curve for the curve modifier it moves to the center. How can I fix the problem so that I can have the array going from one end of the curve to the other? Finding the solution of the congruence $4x\equiv16\pmod{26}$ Solve the congruence   $$4x\equiv16\mod{26}.$$  How do I find the solution to this? I have tried by the euclidean algorithm but the gcd is not $1$ so it doesn't work.  $$\begin{align} 26&amp;=&amp;6&amp;\times4&amp;+2\\ 4&amp;=&amp;2&amp;\times2&amp;+0 \end{align}$$  Note: I understand we can see that $4$ and $17$ are solutions but how would I work this out algorithmically? I'm from Central Pennsylvania, and apparently, we have a strange language construct in this area. I was recently talking about how "my car needs washed" to a friend from NJ, and she told me that my sentence was grammatically incorrect.   I realize she's right, and I realize my options are "my car needs to be washed" or "my car needs washing". But I'm not clear on the precise rule being invoked. How do I get rid of "U3 System" on my USB drive? I have a USB drive (SanDisk SDCZ40-016G) that mounts in a way I've never seen before. When inserted, two items appear in Places -> Computer:    "SanDisk Ultra Backup: 16GB" contains my data, and "CD Drive: U3 System" contains a Windows executable. The part with the Windows executable doesn't look useful to me so I'd like to remove it. I used GParted to delete the only partition listed on the device and then I created and formatted a new partition:    Strangely, the "CD Drive" containing the Windows executable was perfectly intact after this operation.  What's going on?