CRED: post_excerpt field overrun window

Dear Support Team, post_excerpt field in CRED form overrun window via mobile phone. Kindly advise how to correct width of field. Unfortunately CSS doesn't have effect:

<div class="cred-field cred-field-post_excerpt">
<div class="cred-label">Message</div>
[cred_field field="post_excerpt" post="sobytie" value="" urlparam=""]
</div>

CSS:
@media screen and (max-width: 720px) {

.cred-field cred-field-post_excerpt {
width: 90%;
}

Thank you in advance
Anton