I will throw in a few more examples and some context:
<style>
.wsite-menu-default li:last-child a {
font-weight: bold; /*sets the text to bold*/
font-weight: 500; /*there are "levels" to boldness and thickness (https://www.w3schools.com/cssref/tryit.asp?filename=trycss_font-weight)*/ font-size: 15px; /*sets the size, higher pixels = larger text. Other values can be used (pt for print media as an example) but px is the basic standard*/
/*Other areas of possible interest*/
text-decoration: underline; /*underlines the text, you can also do things like strikethroughs*/
color: red; /*sets the text color*/
background-color: blue; /*sets the background color*/
background-color: rgba(224, 78, 57, 0.7); /*sets background color by RGB values with an opacity*/
}
</style>
As you can see, CSS gives you access to near limitless customizability to really let your creativity fly. If you need any more help or some links to reference please let me know 
Sure thing, always happy to help out where I can.
My best guess for that is that the styling is getting caught up in your cache. Browsers like saving styles for easy loading so it doesn't have to re-download every little piece every single time. If you're on Chrome you can do CTRL + SHIFT + R or CTRL + F5 as a keyboard shortcut to clear the cache. On IE I think the CTRL + F5 will do it too. If that doesn't work you can normally access the cache reset somewhere in the history settings (again, thinking in terms of Chrome here).
I think that will solve the issue but I'm curious to see if the problem is persistent. Best of luck 
@sleepwalker021, I should have looked at your site again! I know what the problem is here. CSS or Cascading Style Sheets function like a waterfall, changes flow down the style sheet. So if you have something mentioned twice over, the final mention will take precendence. Attached is a view from the Chrome Dev Tools (tools built into Chrome to allow you to see styling and other processes that are running on web pages)
Here you can see your "lightblue" has a strikethrough. This indicates that the style was there initially and is now overwritten by the blue that is there above. Did you perhaps paste this code snippet twice? It appears to be the case considering there are two separate instances of:
.wsite-menu-default li:last-child a
You need only to remove that second call you had and merge the styles you want to keep. As an aside, the yellow warning symbol means incorrect grammar, you need to change "font-style" to "font-weight" in order for the style to apply correctly. CSS can trip you up in so many ways in how they choose to reference certain things. So at the end of this post what you get is:
.wsite-menu-default li:last-child a {
border: solid;
font-weight: 700;
text-decoration: underline;
color: black;
background-color: lightblue;
}Let me know if you are still having problems with it.
@sleepwalker021 I tried to post but it looks like I bungled something. I'll spare you the build up that went into my other post:
CSS or Cascading Style Sheets flow down like a waterfall, so if you mention something twice the second mention will take precedence. See below:
You can see here (Chrome Dev Tools) shows that the reference to the last child element is being referenced twice with the one that includes blue being called last. Check to see that you didn't accidentally paste it in again somewhere. Find what you need and merge the styles together into one class.
.wsite-menu-default li:last-child a {
border: solid;
font-weight: 700;
text-decoration: underline;
color: black;
background-color: lightblue;
}
Let me know how it goes.
