There are a number of things that will limit your sites presence in the search engines. First and foremost is conent that the SE’s can read. Many can now read PDF Files and some multi media files, others can’t. Here are a few of the things that they can not read, yet.
Graphics – Graphcs are meaningless except for the file name, and any alt tags that are added to the html code that puts the graphic on the page. File names are important. A graphic labeled icon1.jpg is not going to be indexed by the SE’s very well. Now a graphic with a name of Band-Schedule.jpg is going to be read by the SE’s. Add to that an alt tag in the code that says Click here to see the Bands Current Schedule of upcoming shows, and you have added readable content by the SE’s that help your site.
Java Script – Java script is meaningless and in many cases can halt SE’s dead in their tracks. If you need to use Java it is best to have it in a separate file and use an include or some other means of bringing the script into the code of the page.
Style Information – many people, and software, put style information in the page. This is code that tells the browser how to show various things on a page. This information again is better used in an external file that is called upon by the page in it’s code so that it doesn’t confuse the SE’s
Outdated Code – there are updates made to the code that is used to create websites. It is important to try to remain as close to W3C Complaint in your code as you can. No site is perfect, but the better you are the better you show up. This is dual effective. First is that the customers will all generally see the page the same way regardless of the kind of browser or computer they are using. Second is that it shows the SE’s that your using proper code in your site.
Frames - frames are an old way of trying to control where things show up on a page. While the code is still valid, it isn’t easy for SE’s to see your site properly. It is far superior to use tables and nest them together to get control over the content, and the look will be the same, but the SE’s will read it better.
Those are just a few of the Don’ts that you should avoid in your website design.
Sparky