I am learning jQuery and new to it. I was trying to run some code but it was not running and then I found that I just need to give one space before ending double commas/quotes "

```
$("div:not([id=header]) " + strWhichTag).each(function(){
    //some function          
});

```

Now the question is that **why do we need to give space after id=header])** if I remove that space and use this code, it doesn't work, the code below doesn't work but Why

```
$("div:not([id=header])" + strWhichTag).each(function(){
    //some function          
});

```

CHANGES------------------------
strWhichTag is basically h3 but it is not child to #header

**Second thing I need to know is this**

```
var oList = $("<ul id='bookmarksList'>");

```

here can I use single quotes and double quotes alternatively or I need to keep the same level like using double quotes and use sigle quotes inside them

I am learning it so any help will be appriciated