I am struggling to center my H1 tag inside my main tags. If I use position fixed with top:50% and left:50%, it works a bit, though I am never able to center it to the middle. Nothing else will work. Any advice ?    main .container {   margin-top: 40%; }   main .container .row h1 {     text-align: center !important; } &lt;main&gt;         &lt;div class="container"&gt;             &lt;div class="row"&gt;                 &lt;h1&gt;WELCOME&lt;/h1&gt;             &lt;/div&gt;         &lt;/div&gt;     &lt;/main&gt;     Could other elements like a navbar or html interefere with this ? I also have this property for my html:    html {   min-height: 100%;   background-size: cover;   background: linear-gradient(rgba(0, 0, 0, 0.4), rgba(0, 0, 0, 0.5)),   url("/static/images/background.png") no-repeat fixed center center; }     For me it's rendered like this:
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;
How can I prove the Carmichael theorem I am trying to prove that these two definitions of Carmichael function are equivalent.  I am using this definition of Carmichael function:     $\lambda(n)$ is the smallest integer  such that $k^{\lambda(n)}\equiv1 \pmod n\,$ $\forall  k$ such that $\gcd(k,n)=1$.   to prove this one:     $\lambda(n) = \begin{cases}\phi(p^a) &amp; (p=2\text{ and }a\le 2)\text{ or }(p\ge 3)\\\dfrac 1 2 \phi{(2^a)}  &amp; a\ge 3\\ \text{lcm}\left((\lambda(p_1^{a_1}),\cdots,\lambda(p_k^{a_k})\right)&amp; \text{for }n=\prod_{i=1}^k p_i^{a_i} \end{cases}$   Since $a^{\lambda(n)}\equiv 1 \pmod n$,  and $a^{\lambda(m)}\equiv1 \pmod m$ with $\gcd(m,n)=1 \implies a^{\text{lcm}({\lambda(n)},\lambda(m)}\equiv1 \pmod {nm} $   Hence $\lambda (mn)=\text{lcm}(\lambda(n), \lambda(n))$ for $m$ and $n$ coprime to each other.  How can I prove the other relations? I have a 3D truck model already textured and properly imported into Blender. This is a game model and I need to "re-paint" with design from other transport companies. The problem is that I don't have a UV layout (skin template) to serve as a guide for future paintings.  Is there a way to "extract" an UV Layout to .JPG or .PNG to serve as guide for .DDS texture editing?  Please note that I don't want to remap the model. I still want to use the actual UV Mapping and just need to edit the actual textures. In blender cycles render engine, how do I put a movie clip on a plane so it displays the video? I want the video to be on the plane if there is a way. I tried to choose a answer for a question on SA and someone immediately answered with the correct response. I try to click the check box and it says wait 2 min. I keep clicking until it changes from 2 min to 1 min. I wait 60 seconds on my watch and click again and it says please wait 59 seconds.  The 2 minute mark should have said 3 and the 1 minute mark was really 2.  It seems that this has , which is a lot more inconvenient than 59 seconds. using underscore's “difference” method on arrays of objects Implementing support for nested transactions using JDBC 3.0 our legacy application uses JDBC 3.0. it supports transactions by implementing its own transaction manager that is capable of returning the same JDBC connection for each thread. The problem I recently discovered is that it doesn't support nested transactions: if a transaction is started inside an another transaction, then every SQLs running in the context of the inner transaction will be executed using the same db connection, and when it's commited or rolled back it will automatically commit or roll back all the changes starting from the outer transaction.  As far as I understand I can implement the support for nested transaction using JDBC 3.0 savepoints: whenever a nested transaction is started, I can set a new savepoint for the current connection. Afterward, if the nested transaction is rolled back, I will just rollback to this savepoint. If, on the other hand, it is commited, I will just do nothing. Only the commit of the most outer transaction will save the changes to the db.  Is this correct? Does this approach have any flaws? If yes, what are my possibilities?  Thanks. I have a netbook with an AZERTY layout. I've changed it to "bépo" to try it, but now I've reset it to a french layout.  While all the apps have taken the change into account, Ubuntu's login manager still uses bépo, making entering passwords a challenge. I've enabled the virtual keyboard for the time being so that I could login again.  I don't remember what I had done in the first place to switch the login screen to bépo, but now I can't switch it back.    EDIT : In the keyboard settings page, if I click "use system defaults", then everything is in bépo ! Where is this different keyboard layout set ?  ANOTHER EDIT : Here's what did not work :   Changing the layout in settings using the "use system defaults" checkbox in settings sudo dpkg-reconfigure keyboard-configuration changing it in Xconf adding a line in /etc/lightdm/lightdm.conf  sudo dpkg-reconfigure locales slaming head against desk dpkg-reconfigure lightdm sudo gsettings set org.gnome.libgnomekbd.keyboard layouts "['fr']" combinations of the above     Is it possible to relaunch the keyboard configuration tool that's in ubuntu's setup ? The thing has automatic layout detection and it changes the setting everywhere. Deleting self-answered question gets "Delete this answered question" warning While attempting to delete a question which was answered by myself, and with no other answers, I got the following warning:     Delete this answered question?      We do not recommend deleting questions with answers because doing so   deprives future readers of this knowledge.      Repeated deletion of answered questions can result in your account   being blocked from asking. Are you sure you wish to delete?   I understand that deleting your question when someone else has answered it is effectively nullifying the effort that person put into that answer, which is bad. But is it bad if the only answer that's deleted along with your question is your own? Can a shell script set environment variables of the calling shell? I'm trying to write a shell script that, when run, will set some environment variables that will stay set in the caller's shell.  setenv FOO foo   in csh/tcsh, or  export FOO=foo   in sh/bash only set it during the script's execution.  I already know that   source myscript   will run the commands of the script rather than launching a new shell, and that can result in setting the "caller's" environment.  But here's the rub:  I want this script to be callable from either bash or csh.  In other words, I want users of either shell to be able to run my script and have their shell's environment changed.  So 'source' won't work for me, since a user running csh can't source a bash script, and a user running bash can't source a csh script.  Is there any reasonable solution that doesn't involve having to write and maintain TWO versions on the script? Landscape topography from grayscale image Why do I get "Required key not available" when install 3rd party kernel modules or after a kernel upgrade? This issue happens only on UEFI systems with enabled Secure Boot.  When I try to install DKMS modules like VirtualBox, Nvidia, or Broadcom drivers, they do not install and I get Required key not available when I try to modprobe them.  VirtualBox complains that vboxdrv is not loaded.  Broadcom wl driver is shown in lspci -k as a kernel module but is not in use. sudo modprobe wl throws Required key not available.  Also this issue may happen when I install some kernel modules from git sources.  This issue may appear after a kernel update as disabled wireless adapter, black screen after a reboot, etc.   How can I fix it? I've believed for a long time that every Lie group can be decomposed as the semidirect product of a connected Lie group and a discrete Lie group. However, in , it is mentioned that this is not true, and that there exist obstructions to this decomposition. Unfortunately, the level of complexity in the answers goes a bit over my head.  This type of decomposition is also addressed in .  With this loss of faith in my intuition, I have three questions:   Is it true that Lie groups do not necessarily decompose into the semidirect product of a connected group and a discrete group? If this decomposition doesn't always work, then is there a particularly nice argument as to why it doesn't? If this decomposition doesn't always work, then is there a nice example I can use to convince myself that my intuition is wrong?   Edit: As much as I love Qiaochu Yuan's answer, which is thorough and (as usual) a role model among Stack Exchange answers, this is not what I'm looking for. I'm aware of the general extension problem, and that not every short exact sequence splits, but my intuition has led me to think that each Lie group can be decomposed this way. I will certainly play around with his outline for a construction, but I would much prefer a more concrete answer. Once again, thank you!  Edit: As of yet, playing with the construction suggested by Qiaochu hasn't yielded anything interesting. This question is still open to answers! CSS two divs next to each other I'm trying to evaluate $(\hat{a}+\hat{a}^\dagger)^k|n\rangle$ Where $\hat{a}$ and $\hat{a}^\dagger$ are ladder operators and $|n\rangle$ the $n$th Fock state. For this, I separated the problem in three parts: $k&lt;n$, $k=n$ and $k&gt;n$. In this part I'm a bit confused: Is it possible to evaluate such operations? Some tips on how to start would be really great. Pokemon Egg Disappearing So my Pokemon eggs are reaching "maturity" then they just disappear. I don't get a new Pokemon. The egg just disappears. I had this happen with a 2k and a 5k now. Is this happening to anyone else? Fake induction proofs How to delete GRUB entirely from GRUB rescue and boot Windows only How to verify $H\otimes K \cong \bigoplus\limits_{i\in I}H$ Let $H,~K$ be the Hilbert space. if $\{v_{j}\}_{j\in J}\subset H$ and $\{w_{i}\}_{i\in I}\subset K$ are the orthonormal bases, then how to construct the isomorphic mapping: $H\otimes K \rightarrow \bigoplus\limits_{i\in I}H$. Here, the $H \otimes K$ is the tensor product of two Hilbert space. Where do the bipolar jets of black holes come from? I read with interest about Einstein's Theory of Relativity and his proposition about the speed of light being the universal speed limit.    So, if I were to travel in a spacecraft at (practically) the speed of light, would I freeze and stop moving?  Would the universe around me freeze and stop moving?  Who would the time stop for?