The most critical technical web marketing task is making the website accessible to search engines spiders, or robots, that need to crawl through the various pages, images, and other media on your website. To support robot crawlability, the majority of your content should be placed in text structure within HTML tags.
Another way content can be blocked from search engine spiders is if it is placed within Flash. While the use of Flash is trending downward, a large number of websites still employ Flash technology. The use of Flash risks having your content blocked from search spiders.
A more ideal solution is to move away from Flash, which embeds content outside of the robots view, to a solution that allows robots like search engine spiders to view your content. Using jQuery or HTML5 elements can give you control over animations and effects similar to Flash, while still allowing the text to be accessible to search engine spiders.
A final way content can be blocked from search engine spiders is by placing text within an image. Often, designers will place text that needs to be in a special font in an image. The advantage is that the image ensures the text looks the same way to all visitors. Unfortunately, search engine spiders cannot (easily) read the text contained in an image. As an alternative, you can use a font from Google's font library. Using a font from the library, will allow the words to be placed in text where they can be accessed by Google while ensuring that all visitors see the content in the appropriate font.
A final consideration when thinking about crawlability is hidden content. For example, it is common practice on websites to place some content behind tabs. However, this type of tab technique can hide your content from Google, which can get you penalized. Google's general rule of thumb is that if the content is hidden but still available to users (for instance, by clicking on a tab), then that is acceptable behavior. If it is hidden and there is no obvious means of a user being able to un-hide the content, then you run the risk of robots not finding the content (as well as users being unable to see the content too).
In Google Search Console, you can use the "Fetch As Google" tool to see your website as Google's spiders see this page. In Google Search Console, click on crawl then click on Fetch As Google.
Input your page's URL then click Fetch. After inputting your page's URL, you can make sure Google can find the content you are expecting Google to find.
Bing also offers an ability to fetch a page on your website as Bingbot. After logging in, go to Diagnostics & Tools, then click on Fetch as Bingbot.
After inputting your URL in the search box, you will see a copy of the content as Bing sees it. You can search through this code to make sure that the most important content you need Bing to find is contained in this output.