I have a div with Gb/F# as id.  For example, and I'd like to make it visible/hidden using jQuery in this way:    var string= "Gb/F#" $("#"+ string).css("visibility", "visible");     But I got error because of that # in the id. How can I solve my problem? I can't even solve the problem in the css file to declare the div characteristics.
What characters/symbols are allowed within the CSS class selectors? I know that the following characters are invalid, but what characters are valid?  ~ ! @ $ % ^ &amp; * ( ) + = , . / ' ; : " ? &gt; &lt; [ ] \ { } | ` #
Is the set of all possible binary strings countable? Determine whether the given sets are countable or uncountable. Justify your answers either with bijections or using results/methods. The set of all possible binary strings. Note a binary string is a sequence of 0s and 1s.  If a binary string consists only of 0s and 1s, then is it even possible to find a bijection for it? Why doesn't the Java SDK installer set JAVA_HOME? I always wondered why I have to manually set the JAVA_HOME environment variable after installing the Java SDK.     JAVA_HOME=c:\Program Files\Java\jdk1.6.0_12   Visual Studio at least provides a batch file to set these kind of environment variables:     call "c:\Program Files\Microsoft Visual   Studio 9.0\VC\vcvarsall.bat"   Does Java have something similar? I'm trying to make a build script that should simply work after installing the Java SDK. I don't want people to mess with environment variables on their PC. Fortunately, I have very few strongly negative interactions with cars (most people generally seem to respect the way I ride), but those that do stick with me for a while.  The scenario is almost always the same. Rude driver approaches, does their rude thing (obscenities, "get off the road," unsafe passing, etc...), then speeds off to annoy the next bicyclist (or more than likely arrives at the next red light).  While this is generally a short interaction, I find that I just don't have a good rest of the ride. I find myself angry at the driver, thinking about what I could have done differently, and just generally being pissed off. Clearly I realize that it is possible I'm a jerk, but given the relative infrequency of these events I'm hoping that's not the case and I'm just riding defensively and this driver is having a bad day.  What can I do to get over (or mitigate) my anger at inconsiderate drivers? Elementary OS PPA gives “The repository does not have a Release file.” error I am running Ubuntu Bionic Beaver. I was trying to download the pantheon desktop environment on Ubuntu and it didn't work so I gave up. Now when I try to download themes or other things from the terminal I get an error code mentioning Elementary OS even though what I am downloading doesn't have to do with Elementary or pantheon. Here is what the terminal says:   jacob@jacob-MacBookPro:~$ sudo apt-add-repository ppa:tista/adapta -y …                                           E: The repository 'http://ppa.launchpad.net/elementary-os/testing/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. E: The repository 'http://ppa.launchpad.net/mpstark/elementary-tweaks-daily/ubuntu bionic Release' does not have a Release file. N: Updating from such a repository can't be done securely, and is therefore disabled by default. N: See apt-secure(8) manpage for repository creation and user configuration details. Why did Dumbledore drink the potion in the attempt to get a Horcrux? When Albus Dumbledore  finally reaches the island with Harry Potter and finds out that you can't get near the potion, he made a cup and drank it. Why couldn't he just have poured the potion on the "floor"? Why couldn't he have made a big cup to hold almost everything inside the basin? I would like to scale an image file for each dimension differently for example 50% of the x dimension or 25% of the y dimension. Thank you very much. How do I (or can I) SELECT DISTINCT on multiple columns? I need to retrieve all rows from a table where 2 columns combined are all different. So I want all the sales that do not have any other sales that happened on the same day for the same price. The sales that are unique based on day and price will get updated to an active status.  So I'm thinking:  UPDATE sales SET status = 'ACTIVE' WHERE id IN (SELECT DISTINCT (saleprice, saledate), id, count(id)              FROM sales              HAVING count = 1)   But my brain hurts going any farther than that. Conditional \endinput I want to prevent processing rest part of a package in case if it is loaded not from lualatex. For some reason I cannot load ifluatex package, so I borrowed definition of \ifluatex from that package and invented the following chunk of code:  \expandafter\ifx\csname luatexversion\endcsname\relax % = not \inluatex   %\typeout{^^J********************** not LuaTeX^^J}   \PackageError{babel}{     ^^J\space\space * Option russianu is intended for LuaTeX only.              ^^J\space\space * Option russian  is used instead.                     }   \relax   \input{russianb.ldf}     \let\@next@action\endinput \else   %\typein{^^J********************** LuaTeX^^J}   \let\@next@action\relax \fi \@next@action   It seemed to work but Is there a better solution. In particular, it is desirable to avoid introduction of \@next@action because it is used the only time.  Just to explain: my goal is to hack babel with option russian to make it working painlessly with LuaLaTeX without any additional hacks (as described, eg, in  and ) Unable to forward search Bash history similarly as with CTRL-r What is the proper way to re-throw an exception in C#? I have a question for you that stems from my partner doing things a different way than I do.  Is it better to do this :  try {     ... } catch (Exception ex) {     ...     throw; }   or this:  try {     ... } catch (Exception ex) {     ...     throw ex; }   Do they do the same thing? Is one better than the other? How to prove $B-A \succeq 0 \Leftrightarrow$ ellipsoid $x^TBx \leq 1$ contains $x^TAx \leq 1$? Assume $A \in \textbf{S}^n_{++}$, an ellipsoid centered at the origin given by $$\mathcal{E}_A = \{x\mid x^TA^{-1}x \leq 1\}$$ Then we have $\mathcal{E}_A \subseteq \mathcal{E}_B $ if and only if $B-A \succeq 0$. This is the proposition in the Boyd &amp; Vandenberghe's  (pages 45-46). The authors gave only the result, without proof. How to prove it? Let's say I want a way to display just the the center 50x50px of an image that's 250x250px in HTML. How can I do that. Also, is there a way to do this for css:url() references?  I'm aware of clip in CSS, but that seems to only work when used with absolute positioning. How to switch from Resident visa to Tourist visa status in the Schengen area? I have a 1-year residence permit from one Schengen country that is now expiring. Upon its expiration, I would like to get my 90/180 days validity as a tourist to stay, or return here as soon as possible.  I understand that the tourist short-stay scheme is based on the 90/180 days "counter". But what happens if my previous stay was not tourism but residence (as searching year). Wouldn't that mean that I can quickly exit and re-enter the Schengen area to activate my tourist stay?   Also, is there a way to change this purpose of stay without exiting the Schengen area? How to make a teleport command that does not work in the Nether? I have a vanilla server 1.8.7 that uses a book to tp players to spawn or to their home (an invisible armor stand with their uuid connected to it). Problem is, if they set home (place their armor stand) in the overworld and go to the nether and try to tp home (activated using a trigger), it sends them to the same co-ordinates in the nether, and most likely kills them.   I did some digging, and there seems to be a dimension parameter, but I can't quite figure out the syntax or how to get it to work.  I updated the command block to:  /tp @a[score_tpHome_min=1,Dimension=0] 68 68 68   I was hoping it would only tp the player when they were in the overworld (Dimension 0), but it seems to be ignoring that parameter in the nether and still teleporting to those co-ordinates in the nether.   I also tried:  /tp @a[score_tpHome_min=1,Dimension:0] 68 68 68   Which is the way other people were using the parameter in other ways, but that gave an error. Cartoon TV Show About Three Kids and Monsters and a "veil" between realms Formula for completing the square? My math teacher said that this was the formula for completing the square.  Original function: $$ax^2 + bx + c$$ Completed square: $$a\left(x + \frac{b}{2a}\right)^2 - \frac{b^2}{4a} + c$$  However, using this formula I'm not getting the same answers that I would get just by determining the stuff myself.  Is this correct? Can I travel to France with Fiktionsbescheinigung (Fiction Certificate) of Germany How do I check if a number is a palindrome?  Any language. Any algorithm. (except the algorithm of making the number a string and then reversing the string). how to sort by the day of the week? I have two files.  file1:  Dave 734.838.9800   Bob 313.123.4567   Carol 248.344.5576   Mary 313.449.1390   Ted 248.496.2204   Alice 616.556.4458      file2:  Bob Tuesday   Carol Monday   Ted Sunday    Alice Wednesday   Dave Thursday     Mary Saturday     I merged the two files.  file3 should look like this:  Name      On-Call     Phone   Carol     MONDAY      248.344.5576   Bob       TUESDAY     313.123.4567   Alice     WEDNESDAY   616.556.4458   Dave      THURSDAY    734.838.9800   Nobody    FRIDAY      634.296.3356   Mary      SATURDAY    313.449.1390   Ted       SUNDAY      248.496.2204     But I cannot get the weekdays to be in order. How do I go about doing that? This may be a generic OOP question. I wanted to do a generic comparison between an interface and an abstract class on the basis of their usage.   When would one want to use an interface and when would one want to use an abstract class?