I'm new to the web engineering and I have done some searching for URL/Domain masking. In my company, my HOD asked one question during meeting and wants the answer in the next meeting. He asked that why are some sites will hide their real file type?  E.g. http://example/examplefolder/page.NET into http://example/examplefolder/page.html. Why the extension of the pages will always end up in html? Is is the reason to prevent some curious outsider from trying to attack the web site? Is this related with URL rewritting?
Many times I see that URL extensions are hidden (e.g. .html, .php), but not all websites do this.  Why do webmasters hide the extension? Is it for security, for the URL to look cleaner, or for some other purpose?
Bottom to top explanation of the Mahalanobis distance? How do I change the hostname without a restart? I want to change the OS hostname but I do not want to restart.  I have edited /etc/hostname but it requires a restart to get implemented. How to avoid this? Prove that if $d \mid n \in \mathbb{N}$, then $\varphi(d) \mid \varphi(n)$. I want to prove that if $d \mid n \in \mathbb{N}$, then $\varphi(d) \mid \varphi(n)$.  It's given that $d \mid n$, so we know that $n = dm$, for some $m \in \mathbb{Z}$. Now, I want to show that $\varphi(d) \mid \varphi(n)$, i.e. that $\varphi(n) = k\varphi(d)$, for some $k \in \mathbb{Z}$. Drawing a blank of where to go from here. How do I get permissions to delete files on Windows 7? I updated my laptop's OS from Windows XP to Windows 7. There are some leftover files from Windows XP on the computer now. If I try deleting them I get the following error:     You need permission to perform this action.      You require permission from S-1-.... to make changes to this folder.   What's weird is that I am logged in with the only user account on this machine and I have administrator privileges. I tried turning UAC off, but I still can't delete the files.  How can I force removal of these files? How to install and run CPUSim 4.0.11 on Ubuntu 18.04 LTS? I'm going according to the steps mentioned on the cs colby .  First, I installed java on my system by typing the following commands-  sudo add-apt-repository ppa:linuxuprising/java sudo apt-get update sudo apt-get install oracle-java10-set-default sudo apt install oracle-java10-set-default     Then, according to the instructions, I downloaded the .zip file, extracted it and then in the terminal typed   java -cp .:richtextfx-fat-0.6.10.jar:reactfx-2.0-MR.jar -jar CPUSim-4.0.11.jar   But this didn't work.  of command 1 terminal.  Here is a screenshot of all the files that are there in the CPUSim folder,   On observing the names of the folders present, I thought that the previous command was wrong. So I tried the following ones,  java -cp .:richtextfx-fat-0.6.10.jar:reactfx-2.0-M4.jar -jar CPUSim-4.0.11.jar java -cp .:richtextfx-0.6.10.jar:reactfx-2.0-M4.jar -jar CPUSim-4.0.11.jar   But none of them seems to work. Now when I click on the CPUSim-4.0.11.jar file, nothing happens. I have just switched to Ubuntu from Windows 10, and have a very little knowledge about how things work here. Please tell me how I could install and run CPUSim 4.0.11 on Ubuntu 18.04 LTS. Suppose that C is a closed convex subset of $\mathbb R^n$ and $x \in \mathbb R^n$. The projection of $\mathbf x$ onto C is the closest point $\mathbf y \in C : \mathbf z = \mathbf y$ minimizes ||$\mathbf z - \mathbf x$||$_2$ over all $\mathbf z \in C$.  (a) Show that the minimum exists.  (b) Show that there is only one minimizer: that is, show that if $\mathbf y_1$ and $\mathbf y_2$ both minimize ||$\mathbf x - \mathbf z$|| then $\mathbf y_1 = \mathbf y_2$   My ideas:  For (a), to show that the minimum exists I will need to show that it is closed and bounded. We already know it's closed because C is a closed convex subset so I just need to show it's bounded. Am I wanting to minimize ||$\mathbf x - \mathbf z$||$_2$? This is just the Euclidean norm which would be $\sqrt{(\mathbf z - \mathbf x)^2}$=$\sqrt{\mathbf z^2 -\mathbf z \mathbf x -\mathbf x \mathbf z + \mathbf x^2}$. I'm not sure where to go from here...  For (b) I want to use proof by contradiction- so I will assume that $\mathbf y_1$ and  $\mathbf y_2$ both minimize the function and then I'll somehow see that they are in fact equal. How do I set up this argument? I'd like to determine the function corresponding to the following power series: $$x + \sum_{n=1}^\infty (-1)^n\frac{1\cdot3\cdot5\cdots(2n-1)}{2\cdot4\cdot6\cdots2n} \frac{x^{2n+1}}{2n+1}, $$ where $|x|&lt;1$. Run MySQLDump without Locking Tables Recover EXT4 partition I was trying to resize my EXT4 partition and something went wrong. I lost it. The space in once consumed is now being represented as Unallocated. How do I recover the partition? Could "them" mean "those"? When using zero as a quantifier, is it correct to use the singular form on the object of the quantifier, or the plural form?  It sounds confusing when I put it that way, but what I mean is: Which is correct?   Your password expires in 0 days. Your password expires in 0 day.   Essentially I suppose I'm asking, does "singular" mean "one" or "the opposite of more than one", as zero is not "plural" in the traditional "more than one" sense?  I'm pretty sure "days" sounds correct, but I can't be sure. I would like to try a different video display driver, but I'm not sure which one I'm currently using.    What's the simple way to see what driver my system is using currently? Optimization when Cost Function Slow to Evaluate I'd like to create a Categorized style in QGIS, classify with it data in a shapefile and then save the shapefile with the new categorized style. Is it possible? How to alter touchpad settings on Ubuntu GNOME 16.04? After upgrading to Ubuntu GNOME 16.04 with GNOME 3.20 I have found that if I tap my touchpad it clicks which is something I do not want due to a faulty touchpad, previously I was able to disable this through the gnome-control-center, but seemingly there is no way to do this any more through there, so how do I do it? Also, even though it is set to false in gsettings and the dconf-editor seemingly for some reason somewhere in the system it is also set to true as it is behaving as such. I am also unable to set natural scrolling or any of the other touchpad settings seemingly, why not? What is DOCTYPE? How to add a script to Startup Applications from the command line? I have a shell script. I want to configure my script to run automatically during startup. I know how to do this from GUI. But I wanted to do this from terminal. How can I do this?  On a primary research I found that the file needs to be moved to /etc/int.d/ directory. But this operation needs sudo permission. I wanted to do this without super user permissions.   I also found that there are files under ~/.config/autostart/ which are having some settings regarding the startup applications. But I don't know how to edit them to achieve this.   Can someone tell me the exact procedure to achieve this? As the question says, I need to edit my /proc/acpi/wakeup file, but when I open it with any text editor, it shows blank file. cat command, on the other hand, displays correct file contents in terminal. When I navigate to that file in file manager, it says it's size is 0 bytes. I'm using Xubuntu 15.04. I'm thoroughly confused. Let $\theta \in R^{n}$. The Fisher Information Matrix is defined as:  $$I(\theta)_{i,j} = -E\left[\frac{\partial^{2} \log(f(X|\theta))}{\partial \theta_{i} \partial \theta_{j}}\bigg|\theta\right]$$  How can I prove the Fisher Information Matrix is positive semidefinite? Prove that $a^{2^n}=1 \mod 2^{n+2}$ I would like to prove that  $$a^{2^n}\equiv 1 \pmod {2^{n+2}}$$  I tried induction but could not get it.  Thank you very much!