From what you’ve given us, it looks like you’re using a font icon (maybe font awesome?) in a css :before or :after pseudo class. If this is the case, the reason your arrow is not showing is because you are not loading the font correctly. Firstly, you need to define the custom font on your page using @font-face. Many font icon sets, like Font Awesome, allow you to @import the css definition from a CDN. Once you have the font available for the page to use, you must define the font family you’re using on the element to which you’re adding the content.
This article may help you: Use Font Awesome Icons in CSS
If it is still not working then you’ll want to make sure that your browser supports custom fonts, most modern browsers do: http://caniuse.com/#search=%40font-face
Next time, please conduct a bit more research before posting a question.
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solved Some thing wrong in my CSS slider