Questions to ask on a simple usability survey

I am going to be running a simple usability survey on the website I maintain at work. These are the questions I am planning to use:
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{{ section on demographic information, how often they have used the website etc.}}

(on a scale of 1-5, with 5 being "strongly agree" and 1 being "strongly disagree")

General

1.I thought that website was easy to use.
2.The website has a very attractive presentation.
3.The website is interesting and engaging.

Content

4.The content on the website is written in clear and simple language.
5.The content is easy to understand and follow.
6.The content is of high quality.

Navigation

7.I found what I was looking for quickly and easily.
8.I found the website unnecessarily complex.
9.The website didn’t always do what I expected it to do.
10.The website is easy to navigate around.
11.I did not know how to find what I was looking for.
12.The organization of the menus seems quite logical.
13.I felt that I had to click too many times to complete typical tasks in the website.
14.The website responds quickly.
15.Using the website is frustrating.

Other Questions:

1.Do you know what this icon means?
Yes
No

2.Would you be interested in participating in further usability testing on the Housing website? A formal usability test would require about an hour of your time and you would receive small gift in return. If you're interested, please leave your email address below:

3.Do you have any other comments about the Housing and Residences website?
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Can you think of any other questions you would want to ask about a typical website? I actually pulled these from a full usability test plan.