How SEO Works: How to rank higher on search engines
Week 2 Blog: Images and non-HTML content
Entering the second week of the internship, I have learned that images and non-HTML content can play a key role to SEO. Optimizing images, Flash file, Java applets and videos for SEO can be just as important as text content. Not only are they visually appealing, but they help drive traffic to websites. These are a few of the tips I have learned:
1. Give images unique names and alt tags: just as keywords describe the written content, a unique image name allows for the spiders to index your images effectively. Don’t name an image 6-9-14IMG01.jpg but rather inqbation-blog-post2.jpg. However, even though the spiders are getting better at rendering non-HTML content such as images, sometimes the search engine might not be able to index the image. Thus, it is important to include an alt tag attribute to images. Then, even if the image can’t be seen, the spiders can index the text inside the alt tag for that image. Make sure all important images (excluding decorative images) have an alt tag. Keep the alt tags descriptive but concise (less than 150 characters).
<img src= “example.jpg” alt= “example”> the alt tag is in orange with “example” being the description
Additionally, Google now has a tool in Webmaster Tools to create a image sitemap to make crawling more easily accessible to images.
2. Keep image files small especially purely decorative images: Page loading speed is crucial to SEO. Search engines such as Google take into account website speed when giving page ranks. Larger image files can drastically reduce the speed. It is a good idea to allow for viewers to click on the image for a larger version in a new window. Image size SHOULD NOT be reduced by reducing dimensions in the source code. Decrease the actual size of the image through an photo editing program or website (Adobe Photoshop, pixlr etc). A good rule of thumb is to keep files less than 70kb. If images are purely decorative, it might be wise to use CSS styling to eliminate them altogether to optimize loading speed.
3. Depending on the need, different types of images files may be optimal. The most common are JPEG, GIF and PNG. JPEG is easily compressed for a clear image and a small file. GIFs are lower quality but are capable of supporting animation and transparency. They are good for decorative icons and simple images since they only support 256 colors. Finally, PNGs support more colors than GIF and are losses (quality doesn’t degrade with edits which occurs with JPEG). PNG-8 files tend to be smaller than PNG-24 files.
4. Supplement your Java applets, Flash files and videos with in text content. For videos one could consider including a transcript if the words are to be indexed.
5. In your robots.txt file use X-Robots-Tag HTTP header directive for your non-HTML content.