I'm trying to make a website which is similar to this . I would like to know how to get the video in the middle of the page. My code looks like this.  iframe {     width:240px;     height:160px;     align: middle;  }   I've also tried this:  iframe {     width:240px;     height:160px;     margin-left: auto;     margin-right: auto; }   But nothing seems to be working.
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;
Notify question OP (and those who marked it a favourite) if an answer has been modified Seriously, I had not noticed e.g. Jeff's edit  had he not also retagged my question. Prove that $\lim_{n\to\infty}a_n\le \lim_{n\to\infty}b_n$ Theorem  Let $\{a_n\}$ and $\{b_n\}$ be convergent real sequences. Assume that there exists a $N\in\mathbb{N}$ so  $a_n\le b_n$ (eq. 1)  for all $n\ge N$. Then  $\lim_{n\to\infty}a_n\le \lim_{n\to\infty}b_n$.  My attempt at proving  Let $a=\lim_{n\to\infty}a_n$ and $b=\lim_{n\to\infty}b_n$. $a$ and $b$ are real numbers because the limit of a sequence of real numbers is a real number (which is a corollary in my textbook). For proof by contradiction, assume  $b&lt;a$.  Let $\epsilon=\frac{a-b}{2}$. Then we can find $N_a,N_b\in\mathbb{N}$ so  $|a-a_n|\le\frac{\epsilon}{2}$ when $n\ge N_a$, (eq. 2)  $|b-b_n|\le\frac{\epsilon}{2}$ when $n\ge N_b$. (eq. 3)  In a textbook I found that I should do the following:  Choose a $n$ so $n\ge\max(N,N_a,N_b$), then eqs. (1-3) are satisfied. Then  $a-\epsilon\le a_n+\frac{\epsilon}{2}-\epsilon$  How do I get that last thing? Is it necessary to do a proof by contradiction or can one do a direct proof? Your answer is in another castle: when is an answer not an answer? Prove: If $a\mid m$ and $b\mid m$ and $\gcd(a,b)=1$ then $ab\mid m$ Prove: If $a\mid m$ and $b\mid m$ and $\gcd(a,b)=1$ then $ab\mid m$  I thought that $m=ab$ but I was given a counterexample in a comment below.  So all I really know is $m=ax$ and $m=by$ for some $x,y \in \mathbb Z$. Also, $a$ and $b$ are relatively prime since $\gcd(a,b)=1$.   One of the comments suggests to use , i.e., $aq+br=1$ for some $q,r\in\mathbb{Z}$. Any more hints?  New to this divisibility/gcd stuff. Thanks in advance! Using apostrophes correctly I've read a great article about the . But there are still some points that are unclear.  Why do we say...   school project but not school's project? car service but not car's service or even cars' service (plural form)? apostrophe usage but not apostrophe's usage or apostrophes' usage? What is DOCTYPE? What is DOCTYPE and why do I want to use it? What are the different DOCTYPEs I can use? What is the difference between standards and quirks mode, and what are some quirks I may run into with differently set DOCTYPEs?   Lastly, what is the proper DOCTYPE that I should be using? Is your mount an enemy of your target in terms of triggering sneak attack? I was working on building a Zorro character and this question came up: if a rogue is riding on a mount, is that mount considered an ally, or, specifically, an "enemy" of your target?  One of the ways Sneak attack can be trigged is...     "... if another enemy of the target is within 5 feet of it, that enemy   isn’t incapacitated, and you don’t have disadvantage on the attack   roll."   My assumption is yes. Every mount I'm aware of has some kind of attack at its disposal, and thus they represent a threat to your target in addition to the increased threat potential they grant you as the rider. Moreover, if a gnome can proc a sneak attack by acting as a distraction, I don't know why a warhorse wouldn't be able to. That said, is there anything in the books or elsewhere that defines what "enemy of the target" is allowed to include? If $f$ is continuous from $ [0,1]$ to itself and $f(0)=0$, $f(1)=1$ and $f(f(x))=x$ then show that $f(x)=x$ for every $ x $ in the domain of function.  I'd like to prove this statement, my idea goes like below:  Suppose that the converse of the statement holds. then without loss of generality, assume that there exists some $c$ in $[0,1]$ such that $d=f(c)&gt;c$. By symmetry, $f(d)=f(f(c))&lt;f(c)=d$. And $f$ is bijective because $f$ has an inverse function in this domain. So $f$ should be strictly increasing function. But on $[c,d]$, $f$ is decreasing. This is a contradiction.  So it should be that $f(x)=x$ on $[0,1]$.  Is this argument right? And I'd like to know another argument which prove this statement. Thank you for your answer in advance :) Easiest process for me to apply textures, created externally, to my models For the first time I'm working with an artist who is going to be creating the textures for the models I create in Blender.  Up till now I had been building the models and the texturing them myself using pre-built textures from websites.  My question is: What is the easiest process for me to apply the textures our artist creates to my model?  Should I give the artist the UV Map from my model, or should I just get textures from the artist and fit them to the UV Map?  Basically I have no idea how this process works in a professional environment. php - insert a variable in an echo string London Heathrow airport - do I need a transit visa? Do megapixels matter with modern sensor technology? One word/phrase to describe the reaction when you eat a very spicy-hot food I've read the discussion here about .  I've also read this one: .  But I did not find any word or phrase that describes the reaction someone has when eating a too spicy-hot food. You know, they tend to sweat, catch their breath, and even sometimes shed tears; due to the spiciness of the food.  So my questions:        What do you say to describe the reaction someone has when being excitedly "suffered" by a very spicy-hot food? In Indonesian, we would call it kepedasan.   What do you say when you get that thing [the answer to question 1] with you, other than the list I enclose below:                Oh, spicy!     My God, it's spicy-hot!                      Is that it? Does OpenSSH support multihop login? Ansible uses OpenSSH as the bottomed network communicative implementation, but does it support multi-hop login?   I mean, if Ansible can login a server directly, but can it log in server_a then from server_a login server_b for config the server_b? Was it just coincidence that Tahir Mahmood went on stage? Can you use two "and"s in a sentence? For example,      I like chocolate, vanilla, and lemon and orange ice cream.    Indicating "lemon and orange" is a combined flavor, as an item in the list needing an initial and. If $2^n - 1$ is prime from some integer $n$, prove that n must also be prime. I would like to see my review audit history Confession: I have been suspended a couple times from reviewing activities.  Partial Redemption: I have become better and better at passing audits.   I'd like to see my recent and distant history with audits.  Even better, I'd like to see my history with the various types of audits.    I'm not sure this has much value beyond self-reflection and self-analysis. I'd like to see if there are patterns to when I was more likely to fail (do I get sloppy after 10 or 20?), or if there are certain types of reviews at which I struggle more (e.g., suggested edit vs close question).  I suspect that if I reviewed my history and revisited audits I failed, I could create rules and rhythms for myself to become a better reviewer. Migrated questions with a nonexistent author should still show the author's name in the questions list I just noticed . Its author doesn't have an account on this site, which makes it show up like this on the homepage:        It looks like a simple thing - but it gets in the way of the 'flow' of the page:        Couldn't we somehow get the author's name, so that migrated questions with authors that don't have an account here still show up, like this:        Much better. Please? Method for determining irreducibles and factorising in $\mathbb Z[\sqrt{d}]$ I know that $\mathbb Z[\sqrt{7}]$ is a UFD, and I can write the equation $(2 + \sqrt{7})(3 - 2\sqrt{7}) = (5 - 2\sqrt{7})(18 + 7\sqrt{7}) $. So clearly these are not all irreducibles. How do I determine which of these aren't irreducible? How do I factor those into irreducibles?  It seems difficult when dealing with $\mathbb Z [\sqrt{d}] $ with $d$ positive, since the norm map isn't as nice (it's not always positive).  Thanks