I want to center a div container on a page, in the css I am using  margin-left:auto;   does not seem to work.  Anything goes here  Thanks
How can I horizontally center a &lt;div&gt; within another &lt;div&gt; using CSS? &lt;div id=&quot;outer&quot;&gt;   &lt;div id=&quot;inner&quot;&gt;Foo foo&lt;/div&gt; &lt;/div&gt;
Understanding DNA match of 1,723 cM Can I gift games from my library? I understand that once a game is in the library it cannot be removed, only hidden.  My question is, can I gift an uninstalled copy of a game to a friend?  I understand that this may be impossible due to legal issues, and that once a game is in the library it stays. I know this is a very common corollary of the class equation. And I know how to do it by using class equation.   But can you do it bu using group action, maybe find a nice set for G to act on? Find missing indexes tool available to find missing indexes in mssql 2008 ? can we find the missing index using Database Engine Tuning Advisor In Visual Studio, I can cycle through my clipboard history by pressing CTRL+SHIFT+V rather than CTRL+V. I believe it's called a clipboard ring. But that feature doesn't seem to exist outside of Visual Studio, at least not with the same key combination. Is there a key stroke combination built in to windows to do the same, i.e. be able to cycle through your clipboard history while pasting? Should I say "She is in the park" or "She is at the park"? Assume $R=(\mathcal{U}_n)_n$ is a sequence of distinct ultrafilters on some set $X$. Since every Hausdorff space has an infinite discrete subspace, there is a subsequence $R=(\mathcal{V}_n)_n$ of $R=(\mathcal{U}_n)_n$ such that $\{\mathcal{V}_n|n \in \mathbb{N} \}$ is a discrete subspace of $\beta X$. In particular, there is a sequence $(A_n)_n$ of sets with $A_n \in \mathcal{V}_m$ if and only if $m =n$. If we let $B_n=A_n - (A_0 \cup...\cup A_{n−1})$, then the sequence $(B_n)_n$ is pairwise disjoint and $B_n \in \mathcal{V}_m$  iff $m=n$. If we let $B =\cup_n B_{2n}$, then $B \in \mathcal{V}_m$ if and only if $m$ is even. In other words, if $B =\{ \mathcal{V} \in βX|B \in \mathcal{V}\}$, then $B$ is a clopen set with $\mathcal{V}_m \in B$ iff $m$ is even. Therefore, we conclude that the sequence $(\mathcal{V}_m)_m$ cannot converge to any point, so the sequence $(\mathcal{U}_n)_n$ cannot converge to any point either.     I would like to know that:      (1) Why "$B_n \in \mathcal{V}_m$  iff $m=n$"? And " $B =\cup_n B_{2n}$, then $B \in \mathcal{V}_m$ if and only if $m$ is even "?      (2)$B$ is a clopen set with $\mathcal{V}_m \in B$ iff $m$ is even How many inventions did Fred and George have? Fred and George Weasley are known for their trouble-making and general &quot;solemnly swearing they are up to no good&quot;. Their antics/adventures give something to smile about and show us not all wizards are as serious as Professor McGonagall and Hermione. This gives them a reputation of being less intelligent and indeed they only achieved three OWLs. However, we also see the twins have quite a brilliant side! Being able to open and successfully run a shop in Diagon Alley without having completed their Hogwarts education is no easy take (IMO, anyway). Their creations helped students get out of class, our heroes out of tight spot, and even stop our enemies execute an evil plot. Ginny may have said it best:  &quot;We’ve been hearing explosions out of their room for ages, but we never thought they were actually making things,&quot; said Ginny. &quot;We thought they just liked the noise.&quot; Harry Potter and the Goblet of Fire  Do we know how many things Fred and George invented? Are there systems in classical mechanics that are provably non-deterministic? I am running logistic regression on a small dataset which looks like this:    After implementing gradient descent and the cost function, I am getting a 100% accuracy in the prediction stage, However I want to be sure that everything is in order so I am trying to plot the decision boundary line which separates the two datasets.  Below I present plots showing the cost function and theta parameters. As can be seen, currently I am printing the decision boundary line incorrectly.    Extracting data  clear all; close all; clc;  alpha = 0.01; num_iters = 1000;  %% Plotting data x1 = linspace(0,3,50); mqtrue = 5; cqtrue = 30; dat1 = mqtrue*x1+5*randn(1,50);  x2 = linspace(7,10,50); dat2 = mqtrue*x2 + (cqtrue + 5*randn(1,50));  x = [x1 x2]'; % X  subplot(2,2,1); dat = [dat1 dat2]'; % Y  scatter(x1, dat1); hold on; scatter(x2, dat2, '*'); hold on; classdata = (dat&gt;40);   Computing Cost, Gradient and plotting  %  Setup the data matrix appropriately, and add ones for the intercept term [m, n] = size(x);  % Add intercept term to x and X_test x = [ones(m, 1) x];  % Initialize fitting parameters theta = zeros(n + 1, 1); %initial_theta = [0.2; 0.2];  J_history = zeros(num_iters, 1);   plot_x = [min(x(:,2))-2,  max(x(:,2))+2]  for iter = 1:num_iters  % Compute and display initial cost and gradient     [cost, grad] = logistic_costFunction(theta, x, classdata);     theta = theta - alpha * grad;     J_history(iter) = cost;      fprintf('Iteration #%d - Cost = %d... \r\n',iter, cost);       subplot(2,2,2);     hold on; grid on;     plot(iter, J_history(iter), '.r');  title(sprintf('Plot of cost against number of iterations. Cost is %g',J_history(iter)));     xlabel('Iterations')     ylabel('MSE')     drawnow      subplot(2,2,3);     grid on;     plot3(theta(1), theta(2), J_history(iter),'o')     title(sprintf('Tita0 = %g, Tita1=%g', theta(1), theta(2)))     xlabel('Tita0')     ylabel('Tita1')     zlabel('Cost')     hold on;     drawnow      subplot(2,2,1);     grid on;         % Calculate the decision boundary line     plot_y = theta(2).*plot_x + theta(1);  % &lt;--- Boundary line      % Plot, and adjust axes for better viewing     plot(plot_x, plot_y)     hold on;     drawnow  end  fprintf('Cost at initial theta (zeros): %f\n', cost); fprintf('Gradient at initial theta (zeros): \n'); fprintf(' %f \n', grad);   The above code is implementing gradient descent correctly (I think) but I am still unable to show the boundary line plot. Any suggestions would be appreciated.    logistic_costFunction.m  function [J, grad] = logistic_costFunction(theta, X, y)      % Initialize some useful values     m = length(y); % number of training examples      grad = zeros(size(theta));      h = sigmoid(X * theta);     J = -(1 / m) * sum( (y .* log(h)) + ((1 - y) .* log(1 - h)) );      for i = 1 : size(theta, 1)         grad(i) = (1 / m) * sum( (h - y) .* X(:, i) );     end  end   EDIT:  As per the below answer by @Esmailian, now I have something like this:  [m, n] = size(x);  x1_class = [ones(m, 1) x1' dat1']; x2_class = [ones(m, 1) x2' dat2'];  x = [x1_class ; x2_class] Dependency injection and Libraries/Frameworks Configure Postfix to use external MX servers for delivery of local mail if user is unknown I have a following setup:   linux box with postfix configured to be responsible for example.com domain domain's MX servers are configured so that mail sent to example.com is sent to google mail servers several user accounts on linux machine exist (same machine also hosts example.com site)   When someone from the outside attempts to send mail to address ending with @example.com, it gets routed to google mail (and there handled appropriately).  When linux machine tries to send mail to outside world, mail is delivered correctly, as reverse dns and spf records are configured correctly, so linux machine is valid mail sender for example.com domain (along with google mail servers).  However, here's the problem. When php application (hosted at linux box) tries to send mail to someuser@example.com (and someuser doesn't exist on linux box), it fails, since it doesn't even consult google mail servers, but postfix smtp locally concludes that "someuser" is unknown.  So, the question is: how do I tell postfix to relay mails sent to @example.com domain to google mail servers (so, to servers specified in MX records), IF and only if a mailbox is not found locally. Is there a way to make RC4 (ARCFOUR) secure, or is it completely broken? I need a method to authenticate a process with another in order to establish interprocess communication between them, to prevent malicious processes from trying to hook onto the system. Currently I just send a password in plaintext between the two processes and the host process just performs a string comparison with its copy of the password, and will disconnect the connecting process if they don't match. It was fine when I was limited to connecting each process on localhost, but obviously this is not secure if someone just happens to have access to a network between each process and could sniff the packets. Do note that I only care about encryption for the password exchange and I don't really need it to secure the communication.  So basically I need a encryption algorithm that doesn't need to protect its contents well but does need to protect its key, and needs to be as fast as possible with minimal RAM usage and I/O overhead. Yes, data exchange is more CPU-bound than I/O bound since the two processes will be doing loads of calculations and they most likely will be connecting through localhost. Now, I came across RC4, which has a throughput of over twice that of AES-128, but it is evident that it has some weaknesses and I have a lot of questions about how to implement it in a secure way.  Well first question - it's in the title. Is RC4 completely broken and should be avoided? I hear a lot of "it is secure if properly used" and then a lot of "use of RC4 is discouraged."  I was planning to keep the plaintext password on both processes and have them SHA-224 hashed, and concatenate the hash with a 32-bit IV as a 256-bit key for RC4. Are there any security risks with this approach? Perhaps I could then hash the concatenated IV and hashed password with SHA-256? I'm well aware that WEP was cracked because it used a 24-bit IV, but a 32-bit IV has over four billion more unique values. Should I avoid incrementing the IV after each packet like WEP?  And when it comes to RC4-drop[n], what is a reasonable value for n? 256, 512, 768 bytes? How would you implement drop n on a library whose only public operation is encrypting a byte array - pass a byte array of length n after the engine is initialized with the key? Would that mean you would have to basically process n empty bytes after every time you change the IV (which happens after every packet)?  Sources:   EDIT: after reading all these excellent responses, I realized how ignorant I sounded about the whole subject. I had no experience with cryptography before this day, and I only was able to read about RC4's risks from the limited Google results that I could barely follow. thank you to everyone who has been patient with me!  Correct me if I'm wrong, but I believe a better solution is to either use AES (which is not slower because re-keying RC4 after each packet is expensive) or an universal message authentication code. I can easily work with AES, but my understanding of MAC is a bit shaky. An IV is only secure if the update sequence is randomized and unpredictable, meaning I would have to send a 128 bit IV for every message that is sent, which can add a 400% overhead to the short, 4 byte packets that are commonly sent by my application. HMAC can add more than twice that amount if SHA-256 is used. I am going to have to investigate this matter further. IMAP: how to move a message from one folder to another (using the IMAP commands, not with the assistance of any other mail package) In a question on "along" vs "alongside", I have seen this question and the correct answer on the web site makes me confused.      The question is: I enjoyed my walk _________________ the river.  a) along b) alongside  I selected "...along the river" as the correct answer, but on the web site it is shown as wrong and the correct answer is "alongside".  How can that be? I still do not agree, because I have studied the difference between the two. "along" is just the right preposition for thin and long places like road, path, street, beach etc".   So, why would the correct answer be "alongside" which simply means "next to"? Do you not think "along" seems to be better fitting?  Regards,  Note: I would be more than gratefull, if somebody show it to me in a video, like "a walk along the river" and "a walk alongside the river". Maybe I can understand the how "a walk along the river" and "a walk alongside the river" would take place. Going through a text file line by line in C I'm starting to write a book on . Since I've been contributing on this tag for a long time, I had the opportunity to read &amp; answer several interesting threads on Stackoverflow related to this technology.  I would like to discuss some of the interesting cases published on Stackoverflow in my book, and I wonder if I could use the images and code shared on those threads in it.  I'm hoping somebody from StackExchange could clarify about the copyright status of the material shared on Stackoverflow questions/answers. Sometimes I create Material Groups to be used as appendable reusable assets. Unfortunately sometimes parameters I want to control using a Group Node's slider are not available for routing to a Group Node's input socket. Some examples of these are the Color Ramp and the Mapping Node.  So here's what I want to do:    Can this be done? If so, how?  Thanks! IBM Slack links broken Are there any infinite series about which we don't know whether it converges or not? Or are the convergence tests exhaustive, so that in the hands of a competent mathematician any series will eventually be shown to converge or diverge? EDIT: People were kind enough to point out that without imposing restrictions on the terms it's trivial to find such &quot;open problem&quot; sequences. So, to clarify, what I had in mind were sequences whose terms are composed of &quot;simple&quot; functions, the kind you would find in an introductory calculus text: exponential, factorial, etc.