How to make the whole website showing in "Arial" font?

How to revise the style.css, making the website showing in "Arial" font?
Two ways aren't successful as follows:
First, paste the code given below in Custom CSS section
(Appearance -> Theme Options -> Styling Options -> Custom CSS) of your dashboard.
Code:
body {
font-family: 'Arial' !important;
}
Follow below link if still not resolved font issue.
http://www.inkthemes.com/community/threads/new-font-throughout-whole-site.13734/

 

In style.css, I've changed Arvo to be Arial. Two questions comes below.
1. In shop page, two products is showed every line instead of previous 3 products.
2. Header greeting is still old font instead of Arial, like Welcome XXXX Log In.
Here is the attached screenshot. How to solve above 2 questions?

 

Hello,

Please provide your website URL to make me better understand.

Thanks & Regards
Pramod

 

No url, I'm trying it on my localhost.
Do you have a better method, which make the website showing in Arial font.

 

Hello,

Please use below custom CSS code.

Code:

div#menu1 a {
font-family: 'Arial';
}

Thanks & Regards
Pramod