Search Engine Optimization (SEO) questions and answers

SEO questions and answers
How does one go about creating a robots.txt file and placing it in a web site? I hear a lot of talk about robots.txt and how important it is for SEO.

Should I hire an SEO or optimize my website myself?
 I really want to get some good rankings for my site but I don't have a lot of money. Can I realistically expect to get some decent rankings without hiring a professional SEO to do it for me?

What is link anchor text? 
I've recently began reading a couple of webmaster forums and I keep seeing people refer to "link anchor text". Can you tell me what it is so I won't feel like I'm in the dark?

Can you explain how Google PageRank works? And how can I find out my site's PageRank? Thanks.
Should I add a Site Map to my website? I was told that a site map can help me get better rankings in Google. Is it true?

How often do I need to submit my site to the major search engines?
 I keep seeing ads that promise to submit my website to thousands of search engines each month for around $20. Is it worth it?

How can I find out how many of my pages have been indexed by Google?
How can I create ebooks and use them to drive traffic to my website? I've heard about other people doing this but I don't know how to get started. Can you give me some pointers?


Why is my site's Google PageRank now 0?
It had been at PR5 for over a year, but since the last update it's been at PR0 and my traffic has dropped by a factor of 10. Please help me figure this out. Thanks.


Should I redirect orphaned pages to my homepage? 
I have several pages with outdated information on them. Is it better to redirect these pages to the homepage or simply remove the links to them?

Should I buy a link on a page with a Google PageRank of 7? 
I have a chance to buy one for $100 / month. Do you think it would help my site enough to justify the cost? I want to be sure I'll get my money's worth.


What do you think of pop-under exchanges? 
I'm having trouble getting visitors to my site, so I'm thinking about trying one. Are they effective?
 
Are Alexa's traffic rankings accurate?
 I'm hearing conflicting stories on this. I use a site's Alexa ranking to decide whether to advertise or exchange links with them.

Why am I getting tons of traffic but no sales from my Pay-Per-Click ads? 
I'm spending almost $600 per month on Pay-Per-Click advertising with very poor results. The ads bring in plenty of visitors, but no one is buying. What can I do to keep from going broke from all those useless (and expensive) clicks?


How many keywords should I use on a page? 
I want to target as many keywords as possible to attract a lot of traffic, yet still have high search engine rankings.
 
What exactly is a "link farm"? 
I requested a link exchange with another site the other day and the webmaster refused. His reason was that I was linking to a link farm. What did he mean by that?

How can I increase the PageRank of my website on Google? 
It's been stuck at 4 for almost a year! Thanks

From an SEO perspective, is it better to use hyphens or underscores to separate keywords in the names of web pages? 
Does it even make a difference which one you use? I want to use the one that will help my pages rank the highest on Google.
 
Can I have two domains pointing at my website?
I have an established website that is well ranked in the search engines. The problem is, when I first created the site, I made the domain name my company name. Now I want to use a different domain name but not lose my rankings.
 
Why did my website drop out of the Google top-10?
 It was listed on the first page of Google's search results for my main key phrase for well over a year, then it suddenly dropped to the bottom of the third page last week. What could be the reason for the dramatic change? I haven't made any major changes to the site recently.

Why aren't all of my links showing up in Google? 
I've managed to arrange quite a few link exchanges in the past couple of months, but only a handful show up when I use the Google Link: command (link:www.mywebsite.com).
 
Why did my site go to PR0 after adding new pages?
 I've been working to increase my Google PageRank, and I just added over a dozen pages to my website all linking back to my home page. My page rank immediately dropped from a 3 to a 0 and I don't understand why.
 
How do we increase our Google rankings? 
Our longest running website has a homepage ranking of PR4. The whole site consists of approximately 9000 pages which cover our products and accessories.
Could you advise as how we can get a ranking here or do we simply have too many pages?

What is your opinion regarding quality linkbacks that have nothing to do with your own site theme or topic?
I've read so many pros and cons regarding this subject, some with accompanying warnings of the wrath of Google. Does it really make any difference whether the links are related or not?