Many people have the wrong idea of having a website redesigned is all about changing images, logos and backgrounds, many clients come to us looking for a high-end web design company without knowing what redesigning an online business really is about and how this can affect the actual ranking of their websites, and that is a fact, many people/companies have their websites redesigned just to see a decrease on visits and a banish from search engines.
Why this happen?
The answer is simple, if you don't keep the structure of the website intact all the work done and all the information, ranking and position on the search engines will be loss forever, it will be like starting all over again and nobody want that to happen. Even worst is the fact that many web design companies have no idea about keeping structures and they just create a new website without thinking in the consequences for the customer.
Web standards, I'm sure you heard about Web 2.0 and the beautiful things about these concepts, many web design companies talk and speculate about this idea, but, do they really know what they are talking about? Some time ago I hear a person explaining to a customer that Web 2.0 was about gradient colors and big fonts, No kidding... This happen in the web development market because there is a lot of wannabies with no idea about what this profession is about and no interest in learn it, for them it is just a game in which you pay to see.
So what can I do?
First, you need to know the structure of your website, you can go to Google and check all the links your website have with them by using the following command; site:yourwebsite.com, check and take note of all those pages and make sure your new site have them all with content and well formatted.
Second, check all incoming in links your website already have, this is very important, Google and other robots don't like to come to your site referred by another website just to find a 404 error page, again, make sure the website have those links and pages after the redesign is done. To check the websites linking to yours go to Google and type; link: yourwebsite.com.
Third, check CSS standards and usage, this is super easy and you don't need too much knowledge about HTML to know what is going on, depending on your browser right click on the site and go to the option "view source" a new editor will open displaying the actual HTML code of the site, there you can see if exists any reference to CSS, or STYLE tags in the code, just search for .css or style=.
Fourth, Table less coding. Table-less code makes your site look optimized and well formatted in any browser, this is fundamental and a big advantage for your visitors and, never the less, ensures a well recognition of the content for search engines robots which is translated in better ranking and positions.
There could be also pages on your site you don't need any more or just wanted to get rid of them, don't just leave it to the providence, ask your web developers team to redirect those pages to a main page using a 301 or 302 redirection methods.
Just keep in mind that all depend of the grade of knowledge and commitment the selected freelance web development have with their customers, make sure you select the right company to take care your online business. After all, the only one affected with a good or bad decision will be you.